No data fetched from API if URL in config doesn't end with a slash

[pmartin]

If the URL in the config.json file doesn't end with a /, all calls to server fail and no data is ever fetched. And no error is displayed: the screen just remains blank, without any entry.

This is because the URLs for all API calls are built concatenating the URL from the config file and the endpoint path, without adding a / in between.

So: if there is no / at the end of the URL, we must add one.

[pmartin]

Reported by David Sferruzza