8277d7e037
Restore the BM_vert_is_edge_pair(v) check that was present prior to
!134017. In that PR, the edge pair check was moved up, to a previous
iteration pass, that checked the angle thresholds. However, even though
pairs were checked before, the process of performing edge merges might
change a neighboring vert such that it is no longer an edge pair.
Therefore it is necessary to check a second time.
Resolves regression in [0].
[0]: e418f7b1f1