Fix php8.2 deprecation

 - mb_strwidth(): Passing null to parameter laravel#1 ($string) of type string is deprecated

Author: tivvie

src/Illuminate/Support/Str.php

@@ -713,6 +713,10 @@ public static function length($value, $encoding = null)
      */
     public static function limit($value, $limit = 100, $end = '...', $preserveWords = false)
     {
+        if ($value === null) {
+            return $value;
+        }
+
         if (mb_strwidth($value, 'UTF-8') <= $limit) {
             return $value;
         }