bug report about studio 2: can't cover loaded file in current window with new model file

[Racheljia1989]

As showed above,when I tried to load new file cover current opened model file with new file,I failed.The graphwalker log shows me this:2021-06-18 11:51:03.450 DEBUG 17920 --- [nio-9090-exec-2] o.s.web.servlet.DispatcherServlet : Completed 304 NOT_MODIFIED
11:51:03.450 [http-nio-9090-exec-2] DEBUG o.s.web.servlet.DispatcherServlet - Completed 304 NOT_MODIFIED