Re-opening editor for archive entry after restart fails with Eclipse 4.2 M5

[rherrmann]

The following message is shown in the editor area and logged in the error log:

Factory com.codeaffine.archive.ui.internal.editor.PersistableEditorInputFactory returned null from createElement for editor id=org.eclipse.ui.DefaultTextEditor name=.eclipseproduct

The PersistableEditorInputFactory doesn't actually persist the editor input. It is only stored in a map in memory that is of course lost after restart. Hence PersistableEditorInputFactory::createElement returns null for all reqests made by the IDE in order to restore previously opened editors.

With Eclipse 3.x, calls to createElement() that returned null were silently ignored.