Fix #26099: Crash when opening score and pressing direction key

[mathesoncalum]

Resolves: #26099

Problem is as follows:


1. When opening a score via keyboard, we select the “first element in the score”.

2. In scores with more than one staff, the first element in the score is a barline (an element with grips)

3. We call NotationInteraction::nudgeAnchors which causes a crash because NotationInteraction::startEditGrip was never called.

The solution I've gone for in this PR is to check whether a grip edit has started before calling nudgeAnchors. We could potentially include an additional step where we immediately start editing the barline's grips on open - but my feeling is that this behaviour is probably undesirable (see video).

grips.mov

[mathesoncalum]

Oh and for some additional fun - this crash isn't actually reachable in debug builds due to an assertion failure in PlaybackController::seek (but that's a separate issue).

[DmitryArefiev]

Tested #26099 on Win10, Mac13.6, LinuxUbuntu24.04.1 LTS - FIXED