#61 connect already connected vertices can crash app when ...

[Dominique B.]

new scene, create cube, vertex submode, select 2
vertices on the same edge and weld them, select two
other vertices which are on a same edge (thus already
connected) and apply connect on them: app crashes with
several error messageboxes.

The bug might be more general, as i've already seens
these type of crash under other circumstances, but
wan't able to reproduce it - was related with 'convert
to mesh'.