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/SemaDeclObjC.cpp b/lib/Sema/SemaDeclObjC.cpp
index 13655ba..35faa4a 100644
--- a/lib/Sema/SemaDeclObjC.cpp
+++ b/lib/Sema/SemaDeclObjC.cpp
@@ -1651,7 +1651,7 @@
     Params.push_back(Param);
   }
 
-  ObjCMethod->setMethodParams(Context, &Params[0], Sel.getNumArgs());
+  ObjCMethod->setMethodParams(Context, Params.data(), Sel.getNumArgs());
   ObjCMethod->setObjCDeclQualifier(
     CvtQTToAstBitMask(ReturnQT.getObjCDeclQualifier()));
   const ObjCMethodDecl *PrevMethod = 0;