Created attachment 97106 [details]
Backtrace for project from scratch

Hi J-B,
I tried testing the new keyframes for brightness etc. but as soon as I try to create one I get a segfault. At first I thought this happens because I converted an old project but then I  started from scratch and got the same result. 
There were some additional warnings in the converted project saying that an effect can't be deleted. I'll attach logs and screencasts for both tries. 
If you need the project files or source video let me know. 

Software: 
mlt 0.9.8
kdenlive git master efa60d4
movit git (not used)

Steps to reproduce: 
1. Create a new project
2. Add clip to timeline
3. Add brightness effect
4. Double click on the clip to create a new keyframe
5. segfault