[clang] Add invalid check in NormalizedConstraint::fromConstraintExpr. (#86943)

This is an oversight spot in #86869, we should always check the invalid
bit after constructing the `Sema::InstantiatingTemplate` RAII object.

Author: hokein

clang/lib/Sema/SemaConcept.cpp

@@ -1356,6 +1356,8 @@ NormalizedConstraint::fromConstraintExpr(Sema &S, NamedDecl *D, const Expr *E) {
           S, CSE->getExprLoc(),
           Sema::InstantiatingTemplate::ConstraintNormalization{}, D,
           CSE->getSourceRange());
+      if (Inst.isInvalid())
+        return std::nullopt;
       // C++ [temp.constr.normal]p1.1
       // [...]
       // The normal form of an id-expression of the form C<A1, A2, ..., AN>,