[clangd][tests] Fix delimiter handling

Empty line shouldn't be considered a delimiter

Differential Revision: https://reviews.llvm.org/D45764

llvm-svn: 330609
diff --git a/clang-tools-extra/clangd/JSONRPCDispatcher.cpp b/clang-tools-extra/clangd/JSONRPCDispatcher.cpp
index 1e0f5bc..e86b09d 100644
--- a/clang-tools-extra/clangd/JSONRPCDispatcher.cpp
+++ b/clang-tools-extra/clangd/JSONRPCDispatcher.cpp
@@ -278,7 +278,7 @@
       continue;
 
     // found a delimiter
-    if (LineRef.find_first_not_of('-') == llvm::StringRef::npos)
+    if (LineRef.rtrim() == "---")
       break;
 
     JSON += Line;