Multiple personal subscriptions without a send period possible

A user reports:

I was adding a subsription to a filter and accidently managedto subscribe myself twice using 'Personal Subscription'. If I view subscriptions I can see both my subscriptionst o the filter but I am unable to delete either of them or the filter as a whole.

See screenshot for what this looks like. When 'Delete' is clicked, the following error appears in the logs:

org.quartz.SchedulerException: The Scheduler has been shutdown.
at org.quartz.core.QuartzScheduler.validateState(QuartzScheduler.java:415)
at org.quartz.core.QuartzScheduler.unscheduleJob(QuartzScheduler.java:585)
at org.quartz.impl.StdScheduler.unscheduleJob(StdScheduler.java:251)
at
com.atlassian.jira.issue.subscription.DefaultSubscriptionManager.deleteSubscription(DefaultSubscriptionManager.java:123)
at com.atlassian.jira.web.action.filter.ManageFilters.doDelete(ManageFilters.java:67)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at webwork.action.ActionSupport.invokeCommand(ActionSupport.java:415)
at webwork.action.ActionSupport.execute(ActionSupport.java:144)
at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:46)
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:90)
at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:99)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:142)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:58)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:36)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:168)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:181)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
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.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:37)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:72)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36)
at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70)
at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:163)
at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:207)
at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:385)
at com.caucho.server.port.TcpConnection.run(TcpConnection.java:327)
at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:450)
at com.caucho.util.ThreadPool.run(ThreadPool.java:394)
at java.lang.Thread.run(Thread.java:534)