Follow up to c0ad2809231260f24007a39a11ce73fecafddb8a.

diff --git a/lib/message_bus/backends/redis.rb b/lib/message_bus/backends/redis.rb
index ca42a1e..d62bc20 100644
--- a/lib/message_bus/backends/redis.rb
+++ b/lib/message_bus/backends/redis.rb
@@ -320,10 +320,10 @@ LUA
         rescue => error
           @logger.warn "#{error} subscribe failed, reconnecting in 1 second. Call stack #{error.backtrace}"
           sleep 1
-          global_redis.disconnect!
+          global_redis&.disconnect!
           retry
         ensure
-          global_redis.disconnect!
+          global_redis&.disconnect!
         end
       end
 

GitHub sha: 8645edb5