To reproduce this issue:

1. Import case_619848 package
2. Open 'Library' scene
3. Select Dialog( Hallway Right - > Dialog Triggers - > Dialog) in the inspector
4. Notice "Components that are on only some of the selected objects cannot be multi-edited" message even when only a single game object is selected
5. While holding CTRL button also select 'Dialog Triggers'
6. Unity crashes when you select two objects, one with and one without the placeholder component

These objects were got when updating from Unity 4.3.2 to Unity 4.5.1 and nearly all (but not entirely all) of the game objects that contained missing references to scripts now have this message "Components that are on only some of the selected objects cannot be multi-edited"

Captured reproduction: http://screencast.com/t/MVPecA1zp4