Fix reconnect crash

lib/net_base.rb

@@ -63,6 +63,10 @@ class NetBase
     # // TTTTTTTT
     # // TTTTTTTT
     # // TTTTTTTT
+    if @s.nil?
+      puts "Error: no active socket"
+      return
+    end
     flags_bits = PacketFlags.new(opts).bits
     ack = @ack
     ip = @ip

lib/teeworlds_client.rb

@@ -191,8 +191,9 @@ class TeeworldsClient
 
   def disconnect
     puts 'disconnecting.'
-    send_ctrl_close
+    send_ctrl_close unless @s.nil?
     @s&.close
+    @s = nil
     @signal_disconnect = true
   end