pianoroll regression fixes
Fix #21000 - Deleting the last annotation of a segment crashes

In Segment::removeAnnotation(), deleting the last annotation fools the "i != _annotations.end()" look test.
Fixed by adding a break after the deletion.
Merge pull request #336 from mgavioli/Fix_21000_Crash_on_deleting_segm_annotation

Fix #21000 - Deleting the last annotation of a segment causes crash
fix import of OVE file
fix BIAB import
add unit test for BIAB
no QDialog in batch mode
fix button states in Fluid synthesizer UI
fix button states in zerberus UI