[popup] prevent problems if popup is unreferenced during activated signal
[popup] prevent problems if popup is unreferenced during activated signal

Add references to the action and popup around the "activated" and
"action-activated" signals, in case the popup is unreferenced during the
signal emission.

Remove the "captured-event" signal handler during popup dispose to prevent
the handler being called after the popup has been destroyed.

Fixes http://bugzilla.moblin.org/show_bug.cgi?id=6466

jonnylamb/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,clutter-project/mx,clutter-project/mx