Normalize empty params in ActionCable logging

Lograge defaults to empty hashes so we change these to `nil`
so that we won't have type mismatches because these are usually
strings.

config/initializers/lograge.rb

@@ -17,6 +17,13 @@ unless Gitlab::Runtime.sidekiq?
       data[:duration_s] = Gitlab::Utils.ms_to_round_sec(data.delete(:duration)) if data[:duration]
       data.merge!(::Gitlab::Metrics::Subscribers::ActiveRecord.db_counter_payload)
 
+      # Remove empty hashes to prevent type mismatches
+      # These are set to empty hashes in Lograge's ActionCable subscriber
+      # https://github.com/roidrage/lograge/blob/v0.11.2/lib/lograge/log_subscribers/action_cable.rb#L14-L16
+      %i(method path format).each do |key|
+        data[key] = nil if data[key] == {}
+      end
+
       data
     end
 

doc/administration/logs.md

@@ -100,9 +100,9 @@ The ActionCable connection or channel class is used as the `controller`.
 
 ```json
 {
-  "method":{},
-  "path":{},
-  "format":{},
+  "method":null,
+  "path":null,
+  "format":null,
   "controller":"IssuesChannel",
   "action":"subscribe",
   "status":200,