fix: prevent null pointer exception (#135)

Author: supercaracal

lib/redis_client/cluster/node.rb

@@ -232,7 +232,7 @@ def call_multiple_nodes(clients, method, command, args, &block)
           client.send(method, *args, command, &block)
         end
 
-        [results.values, errors]
+        [results&.values, errors]
       end
 
       def call_multiple_nodes!(clients, method, command, args, &block)