Bug Report Screen capture sources let the cursor draw outside of the screen

[codl]

In multi-screen configurations, if the mouse cursor is outside of a screen source, it will still be displayed.

Cropping the source fixes it.

Here's a short video: https://f.codl.fr/1701/cursorescape.mp4
Log: https://gist.github.com/9f726a424100db6c322cd989aaa2e029