Created attachment 106703 [details] the apl model with empty checkpoint condition that crashes amarok amarok allows me to generate an incomplete model of APL using an incomplete "checkpoint" constraint. to reproduce start with for example this APL model : pascal@minipc:~$ cat Musique/classiques3.xml <?xml version="1.0" encoding="UTF-8"?> <playlistgenerator> <generatorpreset title="classiques3"> <constrainttree> <group matchtype="all"> <constraint field="genre" comparison="3" invert="false" type="TagMatch" value="Classical" strictness="0.1"/> </group> </constrainttree> </generatorpreset> </playlistgenerator> then just add a "checkpoint" constraint to the constrainttree (see screenshot) but do not select anything as checkpoint parameters, just adjust strictness of checkpoint to exact click OK the new model is saved when editing this model you see the 2 constraints are there as in the screenshot but when exporting this model to a file the "checkpoint" constraint is absent ! now try to execute this model ==> amarok crashes running in debug mode gives this upon executing this incomplete model : pascal@minipc:~$ amarok: [APG::ConstraintSolver] New ConstraintSolver with serial number 967666005 amarok: [APG::ConstraintNode] new constraint node at 0x31de3f90 with parent at 0x2f6023f0 amarok: [APG::ConstraintSolver] Domain has 4376 tracks amarok: [APG::ConstraintSolver] Running ConstraintSolver 967666005 amarok: Fatal IO error: client killed Unable to start Dr. Konqi Not forwarding the crash to Apport.