Spell empty StringRef correctly (0 is a null StringRef, which is not the same).

llvm-svn: 87011
diff --git a/clang/lib/Sema/CodeCompleteConsumer.cpp b/clang/lib/Sema/CodeCompleteConsumer.cpp
index cb4e8ef..f94989e 100644
--- a/clang/lib/Sema/CodeCompleteConsumer.cpp
+++ b/clang/lib/Sema/CodeCompleteConsumer.cpp
@@ -28,7 +28,7 @@
 // Code completion string implementation
 //===----------------------------------------------------------------------===//
 CodeCompletionString::Chunk::Chunk(ChunkKind Kind, llvm::StringRef Text) 
-  : Kind(Kind), Text(0)
+  : Kind(Kind), Text("")
 {
   switch (Kind) {
   case CK_TypedText: