Blender Git Loki

This fixes
[#25011] Opacity IPO not refreshing with still images

(should be better named: animation of any prefiltering parameters using
still images didn't work out as expected)

And this issue by private mail by Ton:

"I tried to debug a memory-free error; very simple case:

- add image strip
- click on strip at 2 places
- quit blender"