Confluence Cloud APP install error about atlassian-connect.json, ECMA 262 regex "^((?![;|}]).)*$" does not match input string

I want to use Confluence themes module to show background on confluence pages according to the different pages,spaces or users information ,but when I write the Rest API with the Url parameter in the background : url(…) in the descriptor file and install it, an error occurs,as the picture shows.I tried using escape characters, but it didn’t work.

So how do I write a RestAPI address with a url parameter in backgroud:url(…), or is there a better way?

Thank you.