Fix #314910: Cutaway courtesy clefs in 3.6 don't show before time sig…

[elerouxx]

…natures

Resolves: https://musescore.org/en/node/315014

Fixes cutaway courtesy clefs not showing when the EndBarLine segment is not the last segment in the measure. (This happens when there is a time signature or a key signature in next measure, generating timesig/keysig Courtesy segments)

This is an improvement to functionality introduced in PR #6461.

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[MarcSabatella]

I don't know that it is this change in particular, but somehow I do suspect the new code for handling courtesy clefs with respect to cutaway might be responsible for https://musescore.org/en/node/315861. See my comment there.