Problem Editing Navigation

So with the settings set to advanced on my forum's administration panel, when I try to edit the menu pictures for Private Messages in Display->Headers & Navigation, I get this error when I try to click save that says "You must provide a menu name" when clearly there is a locked default menu name that is already provided. So I tried troubleshooting this and I refreshed the page and clicked save without editing anything and I still get the error, I also tried toggling the admin interface and it wont work on either interface.

here's a screen shot of my problem:
https://2img.net/h/i205.photobucket.com/albums/bb236/pbfguppyb/hcez/wtf.jpg

Can your staff fix this? cause the style that I'm using doesn't have an image for PM's and id like for my users to be able to view their PM's.

Thanks!

I am not sure why that comes up.
Although, i have a solution for your problem.
Display>Pics management-Advanced mode
Under the general tab, New Private Messages :Change the Url of the image there.

^ Thanks. This topic really helped me with my problem.