Removing note line 3 of organ crashes MS3

I could reproduce:
1. Range select Measures 1-3 of the 3rd staff
2. Cmd+Delete (Ctrl+Delete)
Results: crash (if not, undo).

Research: most probably the crash happens because of removing the page where the system was placed. Similar crash was observed today on @danieljray's machine during removing stuff from the pages.

Crash log:
0 org.musescore.MuseScore 0x000000010e72d190 Ms::Element::pagePos() const + 16
1 org.musescore.MuseScore 0x000000010e7b443e Ms::LyricsLineSegment::layout() + 1582
2 org.musescore.MuseScore 0x000000010e7b3d77 Ms::LyricsLine::layoutSystem(Ms::System) + 887
3 org.musescore.MuseScore 0x000000010e79aaa6 Ms::Score::layoutSystemElements(Ms::System, Ms::LayoutContext&) + 5670
4 org.musescore.MuseScore 0x000000010e799369 Ms::Score::collectSystem(Ms::LayoutContext&) + 4153
5 org.musescore.MuseScore 0x000000010e79bc7b Ms::LayoutContext::collectPage() + 667
6 org.musescore.MuseScore 0x000000010e79e730 Ms::LayoutContext::layout() + 48
7 org.musescore.MuseScore 0x000000010e79e280 Ms::Score::doLayoutRange(int, int) + 3008
8 org.musescore.MuseScore 0x000000010e6ea0d1 Ms::Score::update() + 385
9 org.musescore.MuseScore 0x000000010e6e9f29 Ms::Score::undoRedo(bool, Ms::EditData) + 105
10 org.musescore.MuseScore 0x000000010e56c0d8 Ms::ScoreView::startUndoRedo(bool) + 40
11 org.musescore.MuseScore 0x000000010e43a52b Ms::MuseScore::undoRedo(bool) + 43
12 org.musescore.MuseScore 0x000000010e44035f Ms::MuseScore::cmd(QAction, QString const&) + 3983
13 org.musescore.MuseScore 0x000000010e43f06d Ms::MuseScore::cmd(QAction) + 1757
14 org.qt-project.QtCore 0x0000000117bd210c QMetaObject::activate(QObject, int, int, void**) + 3132

Actually there are two issues here with a similar result:
1) Removing 3rd staff of Organ (or some other staves) in the given score produces crash.
2) Time delete of the first three measures in the given score produces crash.

These two cases are addressed here: https://github.com/musescore/MuseScore/pull/4496.

Fixed in branch master, commit 5c33610fcc

fix #280668: correct unmanaged spanners handling on time delete

Also don't manually clear systems list from instrument dialog, this
produces crashes too.

Fixed in branch master, commit 42916c1f27

Merge pull request #4496 from dmitrio95/280668-unmanaged-spanners-time

fix #280668: correct unmanaged spanners handling on time delete

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