Comment 500 Error

I enabled comments now that I have enough posts for people to actually read. When I tested it, if I forgot to put the email in the comments form, I got the Internal Server Error 500. I’ve seen this mentioned in the forums but never saw a fix for it. It apparently happens in IE mainly. Is there anyway to make it display, “email required” or whatever?

Thanks. The website is: https://www.fittothefinish.com/blog