send a response when deleting a definition

There's a protocol invariant to preserve here: If a live command sends a
response in any situation, it needs to send a response in all
situations. Otherwise the driver can't decide whether to wait or not.

live.lua

@@ -171,6 +171,7 @@ function live.run(buf)
       love.filesystem.remove(Live.filename[definition_name])
       Live.filename[definition_name] = nil
     end
+    live.send_to_driver('{}')
   elseif cmd == 'GET' then
     local definition_name = buf:match('^%s*%S+%s+(%S+)')
     local val, _ = live.get_binding(definition_name)