Handle the case when a friend approve message no longer exist.

docs/changelog/7.x.x.txt

@@ -24,6 +24,7 @@
  - fixed #12345: tickets in trash still show up
  - fixed #12305: dbSlave breaks WebGUI when not able to connect
  - fixed: Http Proxy assets with no URL to proxy cannot be deleted.
+ - fixed: Friends request messages that no longer exist throw a warning.
 
 7.10.24
  - fixed #12318: asset error causes asset manager to fail

lib/WebGUI/Friends.pm

@@ -96,7 +96,10 @@ sub approveAddRequest {
         status  => 'unread',
         sentBy  => $self->user->userId,
     });
-    $inbox->getMessage($invite->{messageId})->setStatus('completed');
+    my $message = $inbox->getMessage($invite->{messageId});
+    if ($message) {
+        $message->setStatus('completed');
+    }
     $db->deleteRow("friendInvitations", "inviteId", $inviteId);
 }