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/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 47388ac..c533789 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -879,7 +879,8 @@
   translateTemplateArguments(TemplateArgsIn, TemplateArgLocs, TemplateArgs);
 
   QualType Result = CheckTemplateIdType(Template, TemplateLoc, LAngleLoc,
-                                        &TemplateArgs[0], TemplateArgs.size(),
+                                        TemplateArgs.data(),
+                                        TemplateArgs.size(),
                                         RAngleLoc);
   TemplateArgsIn.release();