clang_getCompletionChunkText() will treat optional strings as empty text blocks

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91072 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/CIndex/CIndex.cpp b/tools/CIndex/CIndex.cpp
index 5e8e02d..5c9fb3a 100644
--- a/tools/CIndex/CIndex.cpp
+++ b/tools/CIndex/CIndex.cpp
@@ -1146,7 +1146,7 @@
 
   case CodeCompletionString::CK_Optional:
     // Note: treated as an empty text block.
-    return 0;
+    return "";
   }
 
   // Should be unreachable, but let's be careful.