Blender Git Loki

Fix: VSE seeking with proxy strips would fail on certain frames

If the last decoded frame had the same timestamp as the GOP current
packet, then we would skip over this frame when fast forwarding and we
would seek until the end of the file.

This would could only be triggered reliably in single threaded mode.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11601