Block validation failed

I wrote a specific block for a customer. It is working well. I fill the data. I save and when I look on the website, it is quite perfect. But, when I refresh the editor, I am receiving this error.

WordPress Value of Undefined in Admin

I’m trying to create a basic link control in my WordPress plugin, but I can’t get it to work properly. I ‘ve read the previous answers on here, but still having issues. I also checked out the block-editor component documentation on Github, but the example doesn’t go far enough to address my problem. Here is the code for my Attributes: