Plugin: BigBlueButton: Fix URL when the videoconference server string contains /bigbluebutton at the end *and* we use HTML5 mode

plugin/bbb/lib/bbb_api.php

@@ -224,6 +224,9 @@ class BigBlueButtonBN
 
 		if (isset($joinParams['interface']) && (int) $joinParams['interface'] === BBBPlugin::INTERFACE_HTML5) {
 			$bbbHost = api_remove_trailing_slash(CONFIG_SERVER_URL_WITH_PROTOCOL);
+			if (preg_match('#/bigbluebutton$#', $bbbHost)) {
+			    $bbbHost = preg_replace('#/bigbluebutton$#', '', $bbbHost);
+            }
             $params .= '&redirectClient=true&clientURL='.$bbbHost.'/html5client/join';
         }