The Video importer inspector gives an error and creates an invalid asset if you try to modify settings while the video is playing in the preview pane.

To reproduce:
1. Start the video playing in the preview pane in the inspector
2. Modify a setting
3. Clicking apply
4. Repeat the above with the same setting and a different value

Ideally the inspector should stop the video playing in the preview pane when the user clicks apply. It looks like it tries to do that but something isn't quite happy.

Regressed in 2017.2.0b5