适配 php8

library/think/Loader.php

@@ -613,7 +613,7 @@ class Loader
         if ($type) {
             $name = preg_replace_callback('/_([a-zA-Z])/', function ($match) {
                 return strtoupper($match[1]);
-            }, $name);
+            }, $name ?? '');
 
             return $ucfirst ? ucfirst($name) : lcfirst($name);
         }

library/think/Validate.php

@@ -931,10 +931,10 @@ class Validate
         if (is_string($rule) && strpos($rule, ',')) {
             list($rule, $param) = explode(',', $rule);
         } elseif (is_array($rule)) {
-            $param = isset($rule[1]) ? $rule[1] : null;
+            $param = $rule[1] ?? 0;
             $rule  = $rule[0];
         } else {
-            $param = null;
+            $param = 0;
         }
         return false !== filter_var($value, is_int($rule) ? $rule : filter_id($rule), $param);
     }