Missed one more spot where we needed a to_s

Missed one more spot where we needed a to_s

diff --git a/lib/mobystash/container.rb b/lib/mobystash/container.rb
index 3da7359..d87fb55 100644
--- a/lib/mobystash/container.rb
+++ b/lib/mobystash/container.rb
@@ -222,7 +222,7 @@ module Mobystash
     end
 
     def send_event(msg, stream)
-      @config.log_entries_read_counter.increment(container_name: @name, container_id: @id, stream: stream)
+      @config.log_entries_read_counter.increment(container_name: @name, container_id: @id, stream: stream.to_s)
 
       @llt_mutex.synchronize do
         @last_log_timestamp, msg = msg.chomp.split(' ', 2)

GitHub sha: 9c4dacc0