Blender Git Loki

Fix #29321: Video does not display, gets frozen or flickers

Unfortunately, error was caused by own attempt to deal with some kind of broken
videos when was investigating crashes in sequencer. Issue discovered that time
was related on values stored in timecode index and using them as signed data type
later.

Trying to use unsigned value here leads to signed/unsigned check failures.

Prefer just to pre-process that kind of videos i've been trying to deal with
rather than making more global changes during BCON3.