SUMMARY

When a transparency mask is added to a filter layer and some simple manipulation (like deleting and adding the mask again or going back and forth in Undo History) is performed, Krita crashes.


STEPS TO REPRODUCE
1. Open an image. (In my example it had a size of 5184x3888px.
2. Add a filter layer. (In my case I used up a simple Color Adjustment.)
3. Add a transparency mask to this filter layer.

Now, a few different procedures lead to Krita crashing:
4. Go back a few steps in the Undo History.
5. Go forward again in the Undo History.
6. Delete the transparency mask.
7. Krita crashes. (Video: https://vimeo.com/371430316)

Alternatively:
4. Go back a few steps in the Undo History.
5. Go forward again in the Undo History.
6. Go back again in the Undo History.
7. Go forward again in the Undo History.
8. Krita crashes. (Video: https://vimeo.com/371431930)

Alternatively:
4. Delete the transparency mask.
5. Add the transparency mask.
6. Delete the transparency mask.
7. Add the transparency mask.
8. ...
X. Krita crashes. (Video: https://vimeo.com/371431102)


OBSERVED RESULT

Crash.


EXPECTED RESULT

No crash. :)


SOFTWARE/OS VERSIONS
Linux: Linux Mint 19.1 (based on Ubuntu Bionic)


ADDITIONAL INFORMATION
CPU: Intel© Xeon© CPU E5-2670 0 @ 2.60GHz × 8
GPU: NVIDIA GeForce GTX 1070
OpenCL: activated