Crash on arrow button navigation in horizontal continuous mode

[svetter]

Issue type

Crash or freeze

Description with steps to reproduce

1. Create a new score
2. Change to horizontal continuous mode
3. Press Alt+Right arrow key (Note 'Vertical frame' in status bar)
4. Press Right arrow key

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/81f595ce-0b9f-4de8-bfd8-27be7f455cf2

MuseScore_240827_161220.log

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

db77a84e

Regression

I was unable to check

Operating system

Windows 10

Additional context

No response

Checklist

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

[cbjeukendrup]

What happens here, is the following:

1. Alt+Right selects the "first element of the score", which is the title frame (but it is invisible)
2. Because the frame is selected, it enters "edit mode"
3. Pressing Right results in a call to Box::editDrag; and there, the crash occurs, because system() is nullptr (the title frame is namely not in any frame when in continuous view)

[zacjansheski]

Looks like this occurs in all versions of 4