tree-optimization/106189 - avoid division by zero exception

tree-optimization/106189 - avoid division by zero exception

The diagnostic code can end up with zero sized array elements
with T[][0] and the wide-int code nicely avoids exceptions when
dividing by zero in one codepath but not in another.  The following
fixes the exception by using wide-int in both paths.

	PR tree-optimization/106189
	* gimple-array-bounds.cc (array_bounds_checker::check_mem_ref):
	Divide using offset_ints.

	* gcc.dg/pr106189.c: New testcase.