Bug 437936

SUMMARY

I am unable to pinpoint the cause but I think this happens only with the "sphere dec" interpolation mode in conjunction with changing the color but I think only of the first or last nodes 

STEPS TO REPRODUCE
1. select one of the tail segments
2. change interpolation to "sphere dec"
3. change color of end node

OBSERVED RESULT
crash of krita with a ASSERT error with respect to a QList (See video in additional info)

EXPECTED RESULT
no crash. If the mode is "sphere inc" I notice sometimes a long lag in changing the color of the end node but no crash. It does not seem to crash for segments in the middle if UI play with interpolation mode and color.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: ubuntu 20.04
(available in About System)
KDE Plasma Version: can't make out built from source with build deps from ubuntu repos
KDE Frameworks Version: can't make out built from source with build deps from ubuntu repos
 
Qt Version: 

ADDITIONAL INFORMATION

I have made a video ...

https://drive.google.com/file/d/1ST2Kv9GBRHKGy4d7VRngJfyK4f5ae0Sc/view?usp=sharing

... to demo the bug. It does not appear that splitting of the segments is important to trigger the bug.

git repo details
================
origin	https://invent.kde.org/deiflou/krita.git (fetch)
origin	https://invent.kde.org/deiflou/krita.git (push)
Branch: deiflou/revamp_gradient_editors

git hash of commit when built: 
don't know was merged by dmitry after this and I switched to master. (did not rebuild)