explicitly mark previous as nullable

diff --git a/app/Models/ChatLib.php b/app/Models/ChatLib.php
index c2023946c04bf71ff8817dd1ba322d909c6939e1..f6d7ac942cff5c9d349ccc92c6a57e549bdbae26 100644 (file)
--- a/app/Models/ChatLib.php
+++ b/app/Models/ChatLib.php
@@ -19,7 +19,7 @@ class ChatLib {
                $this->categories = $converted;
        }
 
-       public function addMessage(ChatLog $msg, ChatLog $previous = null) {
+       public function addMessage(ChatLog $msg, ?ChatLog $previous = null) {
                if ($msg->isReply()) {
                        $this->addText($msg->text_content, $msg->getReplyParent());
                } else if (!is_null($previous)) {