Fix crash in Array#-
Fix crash in Array#-

Iterating through the indices to remove and then removing them is not
reliable, because the indices keep changing as you remove elements from
the array. Quite surprising this was only an occasional crash, and not a
consistent one.

kachick/grubby,slawosz/grubby,slawosz/grubby,rajthilakmca/grubby,slawosz/grubby,grubby/grubby,grubby/grubby,rajthilakmca/grubby,rajthilakmca/grubby,kachick/grubby,grubby/grubby,kachick/grubby