Adding a period in "Custom image trigger classes" breaks Drupal

I'm not exactly sure if this belongs here or not. I was fiddling around with custom image classes trying to get it to work on my site. I wasn't seeing the lightbox appear for image classes I entered so I tried placing a period (.) before the name like you would a div class in a style sheet. Eg. ".my-class".

When I did this, all module heading links disappeared and my views slideshow stopped working as well. From the look of it, the javascript code is being altered by placing this period here. This could be just my site but if it is all sites, it might be worth putting a warning somewhere to let people know that they shouldn't place the period before the class name.