If a wacom intuos pro pen is used to click outside of the Color Adjustment Curves window, in the gray area OUTSIDE of the image, Krita enters a weird state. Trying to bring up the Color Adjustment Curves window again then causes Krita to hang (i.e. become unresponsive, covered with white overlay).

If a mouse is used to do the same thing, no problem.

Reproducible: Always

Steps to Reproduce:
0. Wacom Intuos Pro Small 
    * Wacom Control Panel/Driver version: 6.3.11-4
    * Settings: Pen tip = left click, Lower Pen Button (closer to tip) = right click.
    * Everything else disabled (to be explicit: pen eraser, upper pen button, tablet buttons, tablet touchring, tablet touch capability, and tablet wireless capability are all disabled)
    * Settings apply to all applications; no individual applications are identified.

1. Run Krita 2.9.11

2. Create a new file: File > New
    * The new file's dimensions are defined so that there is gray area around the image (I defined a 2048x2048 pixel square image).

3. Brush tool (basic circle) is the active tool

4. Filter > Adjust > color Adjustment Curves: the curves window pops up

5. USING THE WACOM PEN: 
    * Left click (using the tip) on the gray area around the image.
    * The curves window disappears
    * The cursor becomes a black circle with a diagonal slash through it.

6. Try to bring up the curves window again using Filter > Adjust > Color Adjustment curves: Krita hangs, and has to be killed from Windows Task Manager.

Actual Results:  
Krita hangs, and has to be killed from Windows Task Manager. 


Expected Results:  
If step 5 is performed using the mouse instead of the wacom pen,  the curves window disappears, but the cursor is still the regular circle brush cursor (circle). The curves window can be opened again successfully, and nothing bad happens.

Alternate procedure/result:
In step 6, instead of trying to bring up the Adjustment Curve window again, close krita instead
using the X button at the top right. At the prompt to save, click no. Krita will appear to close. 
However, open up Windows Task Manager: in the Processes tab, Krita is still listed as running, and is using a larger amount of memory than usual. If the user tries to run another instance of Krita at this point, it will NOT start the GUI (i.e. it looks like Krita doesn't start anymore). If Krita is killed in the Windows Task Manager Processes tab, Krita can then be started again normally.