Fix issue with Catalyst (Python) editions.

This issue was introduced by commit b8f9e7675. We were now getting an exception
when the animation-scene proxy couldn't be created, which happens in Catalyst.
Fixed that.

Change-Id: Ia32b84b8dfafeaa3931edac57ab5f183092350e5
Merge topic 'fix_catalyst_issue' into next

d0b05d1 Fix issue with Catalyst (Python) editions.