Fix crash with unmet generic type constraints

  It looks like 93dbcf0 didn't completely change
  "(<CallExpression>node).typeArguments" to "typeArguments".

  Closes microsoft#3464

Signed-off-by: David Li <[email protected]>

Author: randombk

src/compiler/checker.ts

@@ -7275,8 +7275,8 @@ module ts {
                 checkApplicableSignature(node, args, candidateForArgumentError, assignableRelation, /*excludeArgument*/ undefined, /*reportErrors*/ true);
             }
             else if (candidateForTypeArgumentError) {
-                if (!isTaggedTemplate && (<CallExpression>node).typeArguments) {
-                    checkTypeArguments(candidateForTypeArgumentError, (<CallExpression>node).typeArguments, [], /*reportErrors*/ true)
+                if (!isTaggedTemplate && typeArguments) {
+                    checkTypeArguments(candidateForTypeArgumentError, typeArguments, [], /*reportErrors*/ true)
                 }
                 else {
                     Debug.assert(resultOfFailedInference.failedTypeParameterIndex >= 0);