Use v.data() instead of &v[0] when SmallVector v might be empty.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72210 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 4becfc8..d2d9a87 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -467,7 +467,7 @@
          "Unexpected number of commas!");
   return Actions.ActOnCXXTypeConstructExpr(DS.getSourceRange(), TypeRep,
                                            LParenLoc, move_arg(Exprs),
-                                           &CommaLocs[0], RParenLoc);
+                                           CommaLocs.data(), RParenLoc);
 }
 
 /// ParseCXXCondition - if/switch/while/for condition expression.