Selecting multiple points while holding Ctrl doesn't work any more

#### Issue details
On previous versions you could move mission points on - Flight Plan tab - by pressing Ctrl and drawing a rectangle around the needed points with left mouse button. The points got red color and one could move them around.
On the current version 1.3.56, this doesn't work any more. I can remember it was working on version 1.5.53 and older.

#### Version
1.3.56

#### Platform
[ x ] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

No source file or test is named. Start by reproducing the issue in the Mission Planner Flight Plan tab on version 1.3.56, using Ctrl and left-mouse rectangle selection around mission points; compare with the reported older behavior. Done means multiple points are selected and highlighted so they can be moved together.

Written by the indexing model from the issue text.