动态bug修复

app/Services/DynamicService.php

@@ -82,7 +82,7 @@ class DynamicService
             }
         }
 
-        if(count($dynamicParam->img_url)>6){
+        if(!empty($dynamicParam->img_url) && count($dynamicParam->img_url)>6){
             throw new Exception("最多上传6张图片");
         }