[clang] [clang][analyzer] Correct SMT Layer for _BitInt cases refutations (PR #143310)

[Balazs Benics via cfe-commits]

================
@@ -570,23 +572,35 @@ class SMTConv {
   // TODO: Refactor to put elsewhere
   static inline QualType getAPSIntType(ASTContext &Ctx,
                                        const llvm::APSInt &Int) {
-    return Ctx.getIntTypeForBitwidth(Int.getBitWidth(), Int.isSigned());
+    QualType Ty;
+    if (!(Ty = Ctx.getIntTypeForBitwidth(Int.getBitWidth(), Int.isSigned()))
+             .isNull())
----------------
steakhal wrote:

Why not using the init-if as I suggested?
```suggestion
    if (QualType Ty = Ctx.getIntTypeForBitwidth(Int.getBitWidth(), Int.isSigned()); !Ty.isNull())
```

https://github.com/llvm/llvm-project/pull/143310