ColorLabel::setColor should emit colorChanged

[SKefalidis]

Resolves: none
Related to: #5922

ColorLabel should emit a colorChanged signal in setColor ( required for PR #5922 )
Without the signal blocks, MuseScore crashes.

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• I made sure the code in the PR follows the coding rules
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• [n\a] I created the test (mtest, vtest, script test) to verify the changes I made

[Spire42]

const bool please.

[SKefalidis]

As you wish :-)

[anatoly-os]

@SKefalidis

Without the signal blocks, MuseScore crashes.

Why? Fixing mysterious crashes by adding random checks is not the best way of writing a software :)

Do you understand the nature of the crash happening?

[SKefalidis]

@anatoly-os The crash happens because MixerDetails::trackColorChanged is called which in turn calls _mti->setColor(col.rgb()); but _mti is empty at this stage.

There are 2 ways to solve this, either add a check in MixerDetails::trackColorChanged (it will also reduce the file size by a few lines) or do what I did (which is consistent with the rest of the file, if you look around every trackColorLabel->setColor is surrounded by instructions to temporarily block signals).

I chose the second way to make sure that nothing breaks (even though the first way should not break something either).