Fix bug breaking 'Repeat Entire Event'

ExternalModule.php

@@ -183,10 +183,11 @@ function setDefaultValues() {
                     // Getting previous event value.
                     // isset returns true for event instances when $prev_event_field_value is equal to an empty string ("").
                     // An additional check to verify the value is not empty is required.
+                    $source_form = ($_GET['instance'] > 1) ? $source_form : "";
                     $prev_event_field_value = $data[$prev_event][$source_field];
                     if (isset($prev_event_field_value) && !empty($prev_event_field_value)) {
                         $default_value = $prev_event_field_value;
-                    } elseif ($data['repeat_instances'][$prev_event][$source_form]) {
+                    } elseif (isset($data['repeat_instances'][$prev_event][$source_form])) {
                         // Handling repeat events by using the most recent instance of the previous event to source values
                         $most_recent_instance = array_slice($data['repeat_instances'][$prev_event][$source_form], -1)[0];
                         $default_value = $most_recent_instance[$source_field];