FIX: Cache missing inline oneboxes (PR #12953)

Some inline oneboxes were not cached when the server did not return an answer for an URL and the queried URL and the absolute URL were different.

For example, if user typed, the client asked the server for and if the server returned an empty response, then the client would keep requesting an inline onebox everytime the composer changed.

In other words, the key used for reading (the absolute URL) and the one used for writing (the URL as typed by the user) were not the same when the server returned an empty response.


(the inline onebox test is failing)