The loopCount function was expecting the left side of a binary op
to always be a symbol, which isn't necessarily the case, so a null
pointer check was added to prevent the crash.

Change-Id: I1fe6626bf52ecbb05664d1d2fa18f7ed830a7ee6
Reviewed-on: https://swiftshader-review.googlesource.com/5344Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>