Crash when moving the end of the Ritardando that spans two lines on the score

[mercuree]

Issue type

Crash or freeze

Description with steps to reproduce

1. Create empty score from Treble clef template
2. Add a Ritardando line to the end of the second system (Second system is important) and extend it into the third system.
3. Using mouse move the end of the marking on the third staff back to the second staff
4. Crash

• Other Gradual Tempo change elements are affected
• Some lines are affected too. I checked trill line, ottava, cresc.
• Regression since Musescore 4.4

Supporting files, videos and screenshots

crash_multiline_elements.mp4

What is the latest version of MuseScore Studio where this issue is present?

MuseScore Studio version (64-bit): 4.6.0-250540307, revision: github-musescore-musescore-9033dc2

Regression

Yes, this used to work in a previous version of MuseScore 4.x

Operating system

windows 10

Additional context

This issue is based on a report from https://musescore.org/en/node/375475 and comment by @cadiz1

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible

[Jojo-Schmitz]

It apparently crashes in isLineSegment(), I suspect gradual tempo change segments are not handled there.
It probably should have gone to isTextLineBaseSegment() instead?

[cbjeukendrup]

Problem seems rather that it's calling Spanner::backSegment() while m_segments is empty.

[Jojo-Schmitz]

Issue is with 4.4.4 (at least) already, so not regression of nightlys