web端无法显示Content-Type为application/json的body

步骤：
1. 连接代理，抓取请求，如果response header中的Content-Type是application/json;charset=utf-8，web端展示response body正常
2. 添加规则，对某一个请求处理response body后，response header中的Content-Type是application/json;charset=utf-8，web端展示response body不正常，展示的是request query param
3. 规则中修改Content-Type为json，web端对response body展示正常，但是连接代理的客户端会不识别

No file or test is named in the issue. Reproduce the two response-body cases through the web interface, compare the response headers and displayed content, and trace how a processed response with Content-Type application/json;charset=utf-8 is selected for rendering; done means the web client shows the response body while the proxy client still recognizes the content type.

Written by the indexing model from the issue text.