Black hatched box in Screenshare

Steps to reproduce:

1. Join a meeting.
2. Open an onscreen tool like Magnifier (which has transparency) and place it where the palette opens up.
3. Open a PowerPoint presentation.
4. Start application share of PowerPoint.

A black box appears at the lower-right corner (where we placed the Magnifier).  If it is an application/window sharing, then that area is seen as hatched.