Crash on load of score with horizontal frame taking an entire system
Ubuntu 14.04, GIT commit: 600306e
1) My First Score
2) click measure 5
3) add / Frames / Insert Horizontal Frame
4) gradually increase size of frame until it pushes all measures to next system
After step 4, if you open the object debugger, you will notice that the system containing frame also contains measure 5 - this is the source of the problem. Measure 5 shows up on both that system and the next. It doesn't cause a crash now, but causes other issues with layout as you might imagine.
I discovered this working on #90766: Issue during creating horizontal frame. This is a simplified case of what I reported in https://musescore.org/en/node/90766#comment-403656. In those steps, I created two adjacent horizontal frames and was assuming this was part of the problem, but it turns out the problem is any time there is a system containing only a single horizontal frame (two adjacent horizontal frames counts as two separate systems).
Basically, we are insisting on adding a measure to the system even though it doesn't fit. Forcing a measure to be added to the first seems to have the intent of the fix for #76006: if insert clef to measure after single-measure system with section break, then should not display courtesy clef, but it isn't appropriate here. So somehow we need to be more careful about this.