fix(assets): proper asset details displaying for .map or other non-module assets

[liangmiQwQ]

Problem

Assets page will display the .map and other assets not created from a chunk, and It can be click but nothing in it like this.

And there is also some error in console (sever-side)

 ERROR  ⬢ RPC error on executing "vite:rolldown:get-asset-details":                                                                        16:56:48
 ERROR  Cannot read properties of undefined (reading 'imports')        

We can't assert assetChunkId is not null and it caused the problem

Fixes

Added some if(..){} to judge if assetChunkId is null, and render differently on the client-side

Now it displays normally especially to Source Map

And there won't be error anymore in the console