Cannot edit an event containing strange characters in the url

[yankedev]

Using v1.7.3, I've been able to create an event using the "-" character of Microsoft office (event url is /events/sa%E2%80%93lsia).

Now I need to edit the event but it fails to validate the url (that cannot be changed anymore)

I got the following error:

sa–lsia
The value should match the following pattern: A-Za-z0-9_- (no spaces, letter or number at the end)

Why I was able to create the event with this url?
Can we allow to change the url of an event?
if the field is disabled, no validation should occour.