fix compatibility with old events

app/models/gitlab_serialize.rb

@@ -1,6 +1,12 @@
 class GitlabSerialize
   # Called to deserialize data to ruby object.
   def load(data)
+    hash = parse_data(data)
+    hash = HashWithIndifferentAccess.new(hash) if hash
+    hash
+  end
+
+  def parse_data(data)
     JSON.load(data)
   rescue JSON::ParserError
     begin