--- a/plugins/libcalendaring/libcalendaring.php	Wed Oct 08 09:33:13 2025 -0400
+++ b/plugins/libcalendaring/libcalendaring.php	Wed Oct 15 14:06:01 2025 -0400
@@ -1446,12 +1446,13 @@
     public static function part_is_vcalendar($part, $message = null)
     {
         // First check if the message is "valid" (i.e. not multipart/report)
-        if ($message) {
+        if ($message && $message->mime_parts) {
             $level = explode('.', $part->mime_id);
 
             while (array_pop($level) !== null) {
-                $parent = $message->mime_parts[join('.', $level) ?: 0];
-                if ($parent->mimetype == 'multipart/report') {
+                $parent = $message->mime_parts[join('.', $level) ?: 0]??null;
+                if (!empty($parent) &&
+		    $parent->mimetype == 'multipart/report') {
                     return false;
                 }
             }