[clang] [Clang][OpenACC] Fixed getExtValue Call on Invalid Gang Dim (PR #221502)

[Shafik Yaghmour via cfe-commits]

================
@@ -2045,7 +2045,7 @@ ExprResult SemaOpenACC::CheckTileSizeExpr(Expr *SizeExpr) {
   // where each tile size is a constant positive integer expression or asterisk.
   if (!ICE || *ICE <= 0) {
----------------
shafik wrote:

Doesn't the `<= 0` check prevent us from getting to the troublesome case here and below? While above the `> 3` condition allows it? 

https://github.com/llvm/llvm-project/pull/221502