Steps to Reproduce

1. Install mono 6.6.0
2. Install subtitle edit portable https://github.com/SubtitleEdit/subtitleedit/releases
3. Install necessary libraries: I have used lasest available versions
   a/ libhunspell-dev
   b/ hunspell
   c/ libtesseract-dev
   d/ libtesseract4
   e/ tesseract-ocr-eng
   f/ mpv
   g/ libmpv-dev
   h/ libmpv1
4. Open Subtitle edit (mono SubtitleEdit.exe). From the top line select Video>Open video file... [and select the file you want to play, in this case a .m2ts file]. Ensure MPV is selected as the movie player in Options

Current Behavior

On selecting the file to play mono crashes.

Expected Behavior

That a video window, inside Subtitle edit would open and the movie start playing.

On which platforms did you notice this

[ ] macOS
[X] Linux Kubuntu 19.10
[ ] Windows

Version Used:
mono 6.6.0

Stacktrace

Please paste the stack trace here if available.

A mono crash report was generated and attached. This was a json file and I have converted it to a txt file type so it can be uploaded.
[mono_crash.12b2f9c488.0.txt](https://github.com/mono/mono/files/4021554/mono_crash.12b2f9c488.0.txt)




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