This issue can be caused by an invalid character being present in the site URL. Can you check your site URL in config.php and make sure it is properly encoded, and does not contain, for example, a space or an invisible character.
Try deleting the entire $CFG->wwwroot line in config.php, and add a new line, and type it into the text editor rather than copying and pasting it.
Try deleting the entire $CFG->wwwroot line in config.php, and add a new line, and type it into the text editor rather than copying and pasting it.