Panning won't stop when mouseup occurs outside drawing area

[AlexHaxe]

Hi,

steps to reproduce (using 2.8.1 demo):

1. select Panning tool
2. press left mouse button and move your drawing
3. while mouse button still pressed leave drawing area (e.g. move mouse to any toolbar area)
4. unpress mouse button
5. select any other tool e.g. Select tool
6. try to select any object -> won't select, instead you can still pan even though Select tool is active in toolbar
7. same for any other tool
8. press Space key -> panning ends, tool functions restored