Fix a possible null pointer dereference found by the analyzer.

When computing the other parameters, ‘op’ is checked for being null before it’s dereferenced.

llvm-svn: 180271

clang/include/clang/AST/Expr.h

@@ -2644,7 +2644,7 @@ protected:
          (ty->isInstantiationDependentType() ||
           (op && op->isInstantiationDependent())),
          (ty->containsUnexpandedParameterPack() ||
-          op->containsUnexpandedParameterPack())),
+          (op && op->containsUnexpandedParameterPack()))),
     Op(op) {
     assert(kind != CK_Invalid && "creating cast with invalid cast kind");
     CastExprBits.Kind = kind;