[0.13.3][Twinsen] Pressing shift interpreted as click while dragging

[Lilly]

Description:
When pressing or releasing shift or ctrl while dragging with the deconstruction planner, this is interpreted as releasing the mouse button.

Reproduction scenario:

1. Select the deconstruction planner.
2. Select some trees, but do not release the mouse button yet.
3. Press and hold shift.
4. Release the mouse button.

Actual result:
After pressing shift in step 3 the selection is finished and the trees will be marked for deconstruction.

Expected result:
Pressing shift switches to "cancel deconstruction" mode, without ending the selection mode.
Releasing the mouse button in step 4 causes deconstruction to be cancelled for the trees in the selection.