Nullpointer exception when doing quick search while adding a link to an issue

I was adding a link to an issue, in the "Link issue" page.
Filled in an issue number in field "Issue".
Then pressed [select issue].
JIRA gave the error message "You have no issues in your current search."
Then I filled in the issue number in QUICK SEARCH and pressed enter.
The result was a nullpointer exception:

java.lang.ClassNotFoundException: class com.atlassian.jira.web.util.HelpUtil : java.lang.NullPointerException
at java.beans.Beans.instantiate(Beans.java:211)
at java.beans.Beans.instantiate(Beans.java:51)
at webwork.view.taglib.BeanTag.doStartTag(BeanTag.java:64)
at _template._standard._help._jspService(_help.java:50)
[SRC:/template/standard/help.jsp:3]
at com.orionserver[Oracle9iAS (9.0.3.0.0) Containers for J2EE].http.OrionHttpJspPage.service(OrionHttpJspPage.java:56)
at oracle.jsp.runtimev2.JspPageTable.service(JspPageTable.java:317)
at oracle.jsp.runtimev2.JspServlet.internalService(JspServlet.java:465)
at oracle.jsp.runtimev2.JspServlet.service(JspServlet.java:379)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ResourceFilterChain.doFilter(ResourceFilterChain.java:65)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:46)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:16)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:84)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:95)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:26)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.AppConsistencyFilter.doFilter(AppConsistencyFilter.java:58)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.EncodingFilter.doFilter(EncodingFilter.java:53)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:556)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.include(ServletRequestDispatcher.java:119)
at webwork.view.taglib.IncludeTag.include(IncludeTag.java:54)
at webwork.view.taglib.ui.ComponentTag.doEndTag(ComponentTag.java:175)
at _decorators._navigator._jspService(_navigator.java:745)
[SRC:/includes/decorators/headerpopups.jsp:38]
at com.orionserver[Oracle9iAS (9.0.3.0.0) Containers for J2EE].http.OrionHttpJspPage.service(OrionHttpJspPage.java:56)
at oracle.jsp.runtimev2.JspPageTable.service(JspPageTable.java:317)
at oracle.jsp.runtimev2.JspServlet.internalService(JspServlet.java:465)
at oracle.jsp.runtimev2.JspServlet.service(JspServlet.java:379)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ResourceFilterChain.doFilter(ResourceFilterChain.java:65)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:46)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:16)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:84)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:95)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:26)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.AppConsistencyFilter.doFilter(AppConsistencyFilter.java:58)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.EncodingFilter.doFilter(EncodingFilter.java:53)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:556)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.include(ServletRequestDispatcher.java:119)
at com.opensymphony.module.sitemesh.filter.PageFilter.applyDecorator(PageFilter.java:169)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:68)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:39)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:16)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:161)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:26)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.AppConsistencyFilter.doFilter(AppConsistencyFilter.java:92)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.EvermindFilterChain.doFilter(EvermindFilterChain.java:20)
at com.atlassian.jira.web.filters.EncodingFilter.doFilter(EncodingFilter.java:53)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:556)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:306)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:767)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.HttpRequestHandler.run(HttpRequestHandler.java:259)
at com.evermind[Oracle9iAS (9.0.3.0.0) Containers for J2EE].server.http.HttpRequestHandler.run(HttpRequestHandler.java:106)
at EDU.oswego.cs.dl.util.concurrent.PooledExecutor$Worker.run(PooledExecutor.java:803)
at java.lang.Thread.run(Thread.java:484)