On importing video using "movieTexture" importer (which was imported successfully with new "VideoClip" importer) ,either Unity stops responding or we get QuickTime crash.

Steps to Repo:
1. Create new project
2. Import any video (.mp4)
3. Select imported video and go to inspector.
4. Select importer Version as "MovieTexture(Deprecated)" and click Apply.

Actual Result:
Video fails to get imported using "MovieTexture".

Expected Result:
Video should get imported successfully with "MovieTexture" importer.

Frequency:
Always

Workaround:
Force Quit and Restart Unity

Environment:
Unity 2017.3.0b8

Reproducible on Windows with Unity Pro/Personal License.

Working fine on Unity 5.5.5f1, Unity5.6.4f1