How do you deal with unrealistic testing failures [on hold]

I'm not sure if this is even the right section to post but..

I have an application form on a website. It's been tested thoroughly and passes. However my client found that if you entered an emoji in one the fields that does an address search, the form breaks.

And my answer is "well, yea." It's an unreasonable action. No user would actually do this, and I think it's silly the client is coming to me about this.

How do I handle/deal with this? Do I tell the client that they're being ridiculous, or do I humor them and fix it?

This isnt the first time they've done this. They'll find all sorts of ways to break the website, such as enter this value, then delete and enter this invalid character, then enter a number, then delete and repeat, separate the red sea and move my house 6 inches to the left and you get an error. And I just feel like puling my hair out. What do they expect?

Who's the unreasonable one here?