Gracefully handle missing style file

Created originally on Bitbucket by johnpeb (John Peberdy)

Leaving Eclipse open for several days on a mac resulted in this. Style files should go somewhere they won't be deleted randomly or javahg should gracefully handle when they go missing.

{{{ com.aragost.javahg.commands.ExecutionException: style not found: /var/folders/h2/n2d4kxdd77s58b69p7cxhr600000gn/T/1344797466334-0/styles/changesets.style at com.aragost.javahg.internals.AbstractCommand.handleReturnCode(AbstractCommand.java:386) at com.aragost.javahg.internals.OutputChannelInputStream.findNextOutputChannelBlock(OutputChannelInputStream.java:179) at com.aragost.javahg.internals.OutputChannelInputStream.(OutputChannelInputStream.java:78) at com.aragost.javahg.internals.Server.runCommand(Server.java:419) at com.aragost.javahg.internals.AbstractCommand.launchStream(AbstractCommand.java:176) at com.aragost.javahg.commands.ParentsCommand.execute(ParentsCommand.java:54) at com.aragost.javahg.WorkingCopy.retrieveParents(WorkingCopy.java:115) at com.aragost.javahg.WorkingCopy.ensureParentsRetrieved(WorkingCopy.java:109) at com.aragost.javahg.WorkingCopy.getParent1(WorkingCopy.java:40) at com.vectrace.MercurialEclipse.commands.HgLogClient.getCurrentChangeset(HgLogClient.java:87) at com.vectrace.MercurialEclipse.team.cache.LocalChangesetCache.getCurrentChangeSet(LocalChangesetCache.java:305) at com.vectrace.MercurialEclipse.ui.CommitFilesChooser.showDiffForSelection(CommitFilesChooser.java:437) at com.vectrace.MercurialEclipse.ui.CommitFilesChooser$4.doubleClick(CommitFilesChooser.java:236) at [...] }}}