web_renderjs_ui: fix detection of Base_redirect redirections

The check was made on the blob response type, which is set from the
Content-Type header returned by the server, but Safari has a different
interpretation of the charset parameter from the mime type, with a
content type set to application/json;charset=utf-8 like Base_redirect
does today, safari creates a blob with type application/json;charset=utf-8
and this was not detected as redirection and the json returned by
Base_redirect was downloaded. Fix this by checking only the essence
of the type.

This also revealed a potential problem when actually downloading json
files, in that case we also check that we have the X-Location header,
that is supposed to be set by Base_redirect before interpreting the json
and when it's not present we force download.

bt5/erp5_web_renderjs_ui/PathTemplateItem/web_page_module/rjs_gadget_erp5_page_form_js.js

@@ -384,7 +384,11 @@ and handling data send&receive.
         .push(function (attachment) {
           var response;
 
-          if (attachment.target.response.type === "application/json") {
+          if (
+            attachment.target.response.type.split(";")[0].trim() ===
+              "application/json" &&
+            attachment.target.getResponseHeader("X-Location")
+          ) {
             // successful form save returns simple redirect and an answer as JSON
             return new RSVP.Queue()
               .push(function () {
@@ -466,14 +470,14 @@ and handling data send&receive.
                   })
                   .push(function () {
                     // Make sure to return nothing (previous render can return
-                    // something) so the successfull handler does not receive
+                    // something) so the successful handler does not receive
                     // anything which it could consider as redirect jio key.
                     return result;
                   });
               });
           }
           // response status > 200 (e.g. 202 "Accepted" or 204 "No Content")
-          // means a sucessful execution of the action but does not carry any data
+          // means a successful execution of the action but does not carry any data
           // XMLHttpRequest automatically inserts Content-Type="text/xml" thus
           // we cannot test based on that
           if (attachment.target.response.size === 0 &&