Make PCHWriter::FlushStmts() robust. If we added null Stmts, reading them back got messed up.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106859 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/PCHWriterStmt.cpp b/lib/Frontend/PCHWriterStmt.cpp
index ef109c3..68b2dae 100644
--- a/lib/Frontend/PCHWriterStmt.cpp
+++ b/lib/Frontend/PCHWriterStmt.cpp
@@ -1185,6 +1185,7 @@
 
     if (!S) {
       Stream.EmitRecord(pch::STMT_NULL_PTR, Record);
+      Stream.EmitRecord(pch::STMT_STOP, Record);
       continue;
     }