Create Issue breaks after upgrade due to custom field upgrade bug

After importing 2.6.1 data into JIRA 3.0 preview on the Setup screen, everything appears to work, except when creating an issue one gets this exception:

java.lang.NullPointerException
at com.atlassian.jira.issue.fields.CustomFieldImpl.populateDefaults(CustomFieldImpl.java:404)
at com.atlassian.jira.web.action.issue.CreateIssue.populateCustomFieldHolderWithDefaults(CreateIssue.java:397)
at com.atlassian.jira.web.action.issue.CreateIssue.doExecute(CreateIssue.java:169)
at webwork.action.ActionSupport.execute(ActionSupport.java:151)
at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:49)
at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:131)
at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:186)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.caucho.server.http.FilterChainServlet.doFilter(FilterChainServlet.java:96)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:129)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:61)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:36)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:168)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.atlassian.jira.web.filters.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:25)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:37)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:72)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36)
at com.caucho.server.http.FilterChainFilter.doFilter(FilterChainFilter.java:88)
at com.caucho.server.http.Invocation.service(Invocation.java:315)
at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java:135)
at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:246)
at com.caucho.server.http.HttpRequest.handleConnection(HttpRequest.java:164)
at com.caucho.server.TcpConnection.run(TcpConnection.java:139)
at java.lang.Thread.run(Thread.java:534)

Also, if the custom fields are viewed, they will have empty Type, Searcher and Default columns.

The workaround is to restart JIRA, as this is a caching bug in the custom field upgrade task.