If MR commits are empty if does not mean compare failed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/services/merge_requests/build_service.rb

@@ -51,7 +51,7 @@ module MergeRequests
         end
       else
         merge_request.can_be_created = false
-        merge_request.compare_failed = true
+        merge_request.compare_failed = false
       end
       merge_request