expr: fix erroneous comparison

as long as `size_t`'s conversion rank is >= `int` this check would work
out fine.

but in case size_t happens to be less than int (which I believe is valid
under the C standard) then comparison will take place in `signed int`
and the operand `-1` will not get implicitly converted to SIZE_MAX.

explicitly cast it to size_t to avoid such issues.

0 files changed, 0 insertions, 0 deletions