[libclang] Make sure the index_data.main_filename field is initialized
in c-index-test. index_enteredMainFile is not invoked when indexing a
module file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165735 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/c-index-test/c-index-test.c b/tools/c-index-test/c-index-test.c
index 97d5751..76e3773 100644
--- a/tools/c-index-test/c-index-test.c
+++ b/tools/c-index-test/c-index-test.c
@@ -2571,6 +2571,7 @@
   index_data.first_check_printed = 0;
   index_data.fail_for_error = 0;
   index_data.abort = 0;
+  index_data.main_filename = "";
 
   index_opts = getIndexOptions();
   idxAction = clang_IndexAction_create(Idx);
@@ -2624,6 +2625,7 @@
   index_data.first_check_printed = 0;
   index_data.fail_for_error = 0;
   index_data.abort = 0;
+  index_data.main_filename = "";
 
   index_opts = getIndexOptions();
   idxAction = clang_IndexAction_create(Idx);