更新

app/Admin/Controllers/DynamicController.php

@@ -33,7 +33,7 @@ class DynamicController extends AdminController
 
         });
         $grid->column('img_url','图片内容')->display(function ($v){
-            if($v){
+            if(isset($v)){
                 $v = json_decode($v,true);
                 $str = '';
                 if(count($v)>0){