Add check if there is no user to borrow license from

classes/webservice.php

@@ -810,7 +810,11 @@ public function provide_license($zoomuserid) {
             if ($this->paid_user_limit_reached()) {
                 $leastrecentlyactivepaiduserid = $this->get_least_recently_active_paid_user_id();
                 // Changes least_recently_active_user to a basic user so we can use their license.
-                $this->make_call("users/$leastrecentlyactivepaiduserid", ['type' => ZOOM_USER_TYPE_BASIC], 'patch');
+                if ($leastrecentlyactivepaiduserid) {
+                    $this->make_call("users/$leastrecentlyactivepaiduserid", ['type' => ZOOM_USER_TYPE_BASIC], 'patch');
+                } else {
+                    throw new moodle_exception('errornousersfound', 'mod_zoom');
+                }
             }
 
             // Changes current user to pro so they can make a meeting.

lang/en/zoom.php

@@ -131,6 +131,7 @@
 $string['err_start_time_past_recurring'] = 'For recurring meetings, the date portion of this field is the earliest possible date for the next meeting. This date must be today or in the future.';
 $string['err_weekly_days'] = 'Select day(s) for the recurring weekly meeting';
 $string['erroraddinstance'] = 'Could not create new zoom meeting. Invalid options selected for a recurring meeting.';
+$string['errornousersfound'] = 'There is no user to borrow license from.';
 $string['errorwebservice'] = 'Zoom webservice error: {$a}.';
 $string['errorwebservice_badrequest'] = 'Zoom received a bad request: {$a}';
 $string['errorwebservice_notfound'] = 'The resource does not exists';