Edited settings.php to set turnitintooltwo/apiurl default setting to null instead of 0. This change aims to address issue turnitin#723 in the upstream repositoty.

Author: lbailey-ucsf

settings.php

@@ -137,7 +137,7 @@
     $settings->add(new admin_setting_configselect('turnitintooltwo/apiurl',
                                     get_string("turnitinapiurl", "turnitintooltwo"),
                                     get_string("turnitinapiurl_desc", "turnitintooltwo").$offlinecomment.$testconnection,
-                                    0, $testoptions));
+                                    null, $testoptions));
 
     // Miscellaneous settings.
     $settings->add(new admin_setting_heading('turnitintooltwo_debugginglogs',