[BUG]Mission Planner crashes on start/stop of Video input from Easycap USBTV007

Hi People

Im experiencing a crash when starting or stopping the Video input.
If selected Via HUD screen, right click, Start camera, it starts correctly as long as no video device is selected.
If I select my video device and press start, I get an error message "Camera Fail: xxx" (Ill post the rest later), and Mission planner crashes instantly.

The Frame grabber used is an Easycap, based on the UTV007 chip.
Driver used is: [OEMDrv.inf.txt](https://github.com/ArduPilot/MissionPlanner/files/2023913/OEMDrv.inf.txt)

Mission planner used is 1.3.56

Please let me know if there is any other information I should provide.

Thank you for the work

Start by reproducing the crash from the HUD screen with an Easycap USBTV007/UTV007 device selected, and capture the complete “Camera Fail” message along with the OEMDrv.inf.txt driver details. Trace the Mission Planner video-input start and stop flow. Done means starting and stopping this device no longer crashes Mission Planner and the failure is handled visibly.

Written by the indexing model from the issue text.