Fix #315627 - Musescore 3.6 crashes when opening large orchestration created in Musescore 3.4.2

[njvdberg]

Resolves: https://musescore.org/en/node/315627

Solve a crash in case nextMeasure() returns a nullptr instead of a pointer to a measure.

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[MarcSabatella]

Seems nextMeasure() will always return nullptr for the last measure. So, why doesn't this crash on every score? What are the conditions that lead to this?

[njvdberg]

The modified check is in Measure::isCutawayClef() and this method returns true if

• 1 An EndBarLine segment is found and this segment and
• 2 This segment has a Clef element and
• 3 The next measure is on the same system.

The original check was:

e && e->isClef() && (nextMeasure()->system() == system()

So, in most cases the nextMeasure() is never called, only when the element is a Clef.

As a matter of fact, the full original check was

e && e->isClef() && (nextMeasure()->system() == system() || toClef(e)->showCourtesy()

This potentially also could cause a crash on toClef(e)->showCourtesy() if the part before the || evaluates to false and e doesn't happens to be an Clef. This also solved by first check whether e is not zero and is a Clef.

[MarcSabatella]

Answering my own question - this happens only if there is a staff whose last measure contains a clef as the last element before the barline. Not an easy thing to make happen, but one way is to add a clef change somewhere then delete all measures after the change. This results in the clef still being present but not visible. I can also get one to be visible by entering a mid-measure clef between two half notes in 4/4 then changing the first to a whole note.

EDIT: posts crossed :-)