Segfault when viewing gamess vibration modes

When I load up a file created by gamess and try to select certain
modes, avo segfaults. See the attached file. Try selecting mode #9,
for instance.

I’ve noticed a reference to this in
VibrationExtension::updateForcesAndFrames(). If I uncomment the sanity
check, I get a nice pop up instead of a segfault – is there a reason
that this check is commented out?