Blender Git Loki

Fix T91992: Incorrect clip strip image size

When proxy size lower than 100% is used, clip strips are rendered with
incorrect image size.

This is because if proxies aren't enabled in movieclip, it automatically
falls back on rendering original media. Sequencer doesn't have knowledge
about this and since 9c99292a16df it assumes that image is proxy,
because it explicitly requested this size.

Check movieclip flag to see if proxies are enabled.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D13080