Fix `Array#sample` with `MRB_INT32`
Array index became potentially negative because `uint32_t` is cast to
`mrb_int`.
@@ -317,7 +317,7 @@ mrb_ary_sample(mrb_state *mrb, mrb_value ary)
for (;;) {
retry:
- r = (mrb_int)rand_uint32(random) % len;
+ r = (mrb_int)(rand_uint32(random) % len);
for (j=0; j<i; j++) {
if (mrb_fixnum(RARRAY_PTR(result)[j]) == r) {
