Blender crashes when selecting a marker in the 3d viewport that is from the non active scene camera. This patch will solve this crash, but introduced a new scenario that isn't thought out. In the new scenario it is still hard to select a marker via the 3d viewport.
I would expect that when selecting a marker in this case would select the camera where the marker belongs to and select the marker that is under the mouse button.
Reviewed By: Sergey Sharybin
Differential Revision: https://developer.blender.org/D6360
79476a9c0a