Crash when copying/pasting a clef into an another clef

I hit this, too, yesterday, also Mac Mojave.

Confirmed, on Windows 7 and with latest master code. Stack trace:
1 ?? 0x4000adf1
2 Ms::ScoreElement::isNote scoreElement.h 260 0xdd3782
3 Ms::Score::select score.cpp 2933 0x8ed112
4 Ms::Score::cmdPaste paste.cpp 990 0x9e5cbe
5 Ms::ScoreView::normalPaste scoreview.cpp 1729 0x447a5c
6 Ms::ScoreView::cmd scoreview.cpp 1805 0x447f20
7 Ms::ScoreView::cmd scoreview.cpp 1770 0x447c3d
8 Ms::MuseScore::cmd musescore.cpp 6264 0x4f7cb6
9 Ms::MuseScore::cmd musescore.cpp 5735 0x4f4f25
10 Ms::MuseScore::qt_static_metacall moc_musescore.cpp 855 0x40a1d6
11 ZN11QMetaObject8activateEP7QObjectiiPPv 0x68c81805
12 Ms::ScoreTab::actionTriggered moc_scoretab.cpp 225 0x41147d
13 Ms::ScoreTab::qt_static_metacall moc_scoretab.cpp 110 0x410fe3
14 ZN11QMetaObject8activateEP7QObjectiiPPv 0x68c81805
15 ZN12QActionGroup7hoveredEP7QAction 0x26574ee5

It is completly unclear to me why testing whether a clef is a note could cause a SIGSEGV (rather than just returning false)

Not only clefs, but also time signatures and key signatures.

Indeed the same issue with time signatures and with the same stack trace. Not with key signatures though, there just an error dialog pops up, "Destination is not a chord or rest"

Here with key signature too.
1) Load this test file: key signature.mscz
2) Copy-paste first key sig on the second one (or the second on the first one)

----> crash

The crash is because the element is not valid, it seems my fix for #288343: Selection lost on paste to single note broke this. Copying a clef on top of a clef works different than copying a note on top of a note.

but e is not NULL

No, it's garbage - already freed memory - because the old clef stayed good in this case. For notes, the new note takes over the old when pasting, but apparently for clefs it's the other way around. Well, need more investigating anyhow.

https://github.com/musescore/MuseScore/pull/5098

Fixed in branch master, commit 2ee0fb2bc3

fix #290187: crash on paste clef/key/time signature

Fixed in branch master, commit 4d3e5f6573

_Merge pull request #5098 from MarcSabatella/290187-crash-paste-single

fix #290187: crash on paste clef/key/time signature_

Automatically closed -- issue fixed for 2 weeks with no activity.