applets/taskmanager: avoid updating dragSource when active is false
grabToImage is async, so when an item is grabbed to an image, the drag
operation can be already cancelled. When dragSource
is not null,
MouseHandler
will always consider the current drag opertion is to move
tasks, which causes the bug.
STR:
- Drag a file onto a task and hold LMB
- Press RMB
- Release RMB
- Release LMB
- Drag a file onto a task again
BUG: 466675 FIXED-IN: 5.27.6