Created attachment 104722 [details]
One of the library files that cause the crash

1. Select several clips and add selection to the library.
2. Create new Kdenlive project.
3. Move the library clip to project bin and then to Timeline.
4. Select the clip on timeline and select "Timeline / Current clip / Expand clip".

This always results in crash:

* * *CREATED PROD:  "/home/fuxoft/.local/share/kdenlive/library/AllTest.mlt"  =  "/home/fuxoft/.local/share/kdenlive/library/AllTest.mlt"
 * *PROXY PATH:  "/home/fuxoft/.cache/kdenlive/proxy/796075dfe88e94c8f2233b78371e5604.mov" ,  "consumer:/home/fuxoft/.local/share/kdenlive/library/AllTest.mlt"
 * * *Setting document xml root:  ""
 * * *Setting document xml root:  ""
originalId:  "7" , newId:  "2"
fixed resource path for producer, newId: "2" resource: "/home/fuxoft/znelka3.wav"
originalId:  "1" , newId:  "3"
fixed resource path for producer, newId: "3" resource: "/home/fuxoft/.cache/kdenlive/proxy/a0669a0e92ad1521d3c54ed54c031913.mov"
originalId:  "2" , newId:  "4"
originalId:  "3" , newId:  "5"
fixed resource path for producer, newId: "5" resource: "/home/fuxoft/.cache/kdenlive/proxy/34b078ca59c928725e9502a0e4b98872.mov"
newId:  "2" , originalId:  "7"
newId:  "3" , originalId:  "1"
newId:  "4" , originalId:  "2"
newId:  "4" , originalId:  "2"
newId:  "5" , originalId:  "3"
 / / / / /WARNING, VIDEO CONTEXT IS NULL!!!!!!!!!!!!!!
* * *CREATED PROD:  "/home/fuxoft/znelka3.wav"  =  "/home/fuxoft/znelka3.wav"
 / // error controller not found, crashing
 / // error controller not found, crashing
 / // error controller not found, crashing
"Cannot insert clip..."
WARNING: bool Phonon::FactoryPrivate::createBackend() phonon backend plugin could not be loaded
WARNING: bool Phonon::FactoryPrivate::createBackend() phonon backend plugin could not be loaded
WARNING: bool Phonon::FactoryPrivate::createBackend() phonon backend plugin could not be loaded
org.kde.knotifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification
org.kde.knotifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification
org.kde.knotifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification
org.kde.knotifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification
 * * *Setting document xml root:  ""

After the crash, Kdenlive is frozen for a while and then I can continue working but the timeline is messed up (e.g. just a single WAV audio is present instead of 5 audio and video clips).

The .MLT file is attached. I tried several times, creating different library clip each time, but the crash happens always. Even before expanding the clip, it isn't exactly identical to the original group of clips when played (e.g. one of the subclips seems to be missing).