Fix a case when the TemplateArgs vector can be empty.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72911 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index dede3bb..c9277aa 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2271,7 +2271,7 @@
   // template.
   llvm::SmallVector<TemplateArgument, 16> ConvertedTemplateArgs;
   if (CheckTemplateArgumentList(ClassTemplate, TemplateNameLoc, LAngleLoc, 
-                                &TemplateArgs[0], TemplateArgs.size(),
+                                TemplateArgs.data(), TemplateArgs.size(),
                                 RAngleLoc, ConvertedTemplateArgs))
     return true;