avoid fall through if entry 13 is set in block SOFTSUSY

Dear Ben,

I noticed a fall through in a switch statement in softpoint.cpp at line 851:  If entry 13 (mAFlag) is set in block SOFTSUSY, entry 14 (tryToConvergeHard) will be set to the same value.

I think this behaviour is not intended and this patch fixes the issue.

Best,
Alex