We got the issue. It happens when an administrator try to input a seller facebook link from back end. But administrator can input his facebook link from back end.
We or our customers didn't face such kind of problem before. Let us found the reason of problem and solve of this issue though we think it's a minor issue because sellers are suppose to fill there facebook link from there store settings.
Near, but not really, the facebook link insert by the seller themselves. when they have facebook link in their account, then i can't update their profile. Thanks and hope you can get back to me as soon as possible.
I'd like to help you. Do you have the latest version of Dokan? If you have the latest version of Dokan, you shouldn't face the above error. I have just tested.
If you're still getting this issue, let me know.
I have tested the issue on your site and got the error. But haven't got anything in my testing environment (Though I'm using the dev version). I believe you've missed something in the theme while customizing. You may replace the theme with the default one and see if the issue solves or not.