特殊字段增加is_null判断

app/AdminAgent/Controllers/ArticleController.php

@@ -96,8 +96,12 @@ class ArticleController extends AdminController
 			//特殊字段处理
 			$form->hidden(['agent_id']);
 			$form->agent_id = Admin::user()->id;
-			$form->sort = $form->sort ?? 255;
-			$form->type = $form->type ? 1 : 0;
+			if (!is_null($form->sort)) {
+				$form->sort = $form->sort ?? 255;
+			}
+			if (!is_null($form->type)) {
+				$form->type = $form->type ? 1 : 0;
+			}
 
 			//不允许编辑的字段
 			$form->ignore(['id', 'created_at', 'updated_at']);