[CRASH] Certain MP4 files cause crash on import attempt

**Commit Hash** (0.2.0-) 1687a721 **Platform** Windows 10 **Summary** (Not super technically savvy, so I apologise) After attempting to import certain MP4 files I've found Olive either outright crashes (not offering a crash report or subsequent menu, simply just closes) or claims the file is unsupported (only in one instance, of the 4 files I'm trying, 3 cause crashes with no subsequent information). I've successfuly loaded some MP4s I know have worked in the past, but as soon as I try to import one of the files causing crashes, a crash occurs every time. I have check the properties of the problem files and confirmed everything is in order, the only correlation I can find is that the problem files have no thumbnail and only show the VLC icon. I don't know if that even means anything to this issue. **Steps to Reproduce** 1. Create new project 2. Import Mp4 file that lacks a thumbnail via any means (drag-drop, import menu, etc.) 3. Either Olive crashes or claims the file is not a compatible format Crash Report (N/A) **Additional Information**