Modal iOS fix

This is so gross. :poop: Some examples of other people with the same problem, and the resulting fix (we're not using Bootstrap, of course, but we implemented our modals in a similar way) are listed below for future reference:
- https://github.com/twbs/bootstrap/issues/9023
- https://github.com/angular-ui/bootstrap/issues/1812
- https://github.com/angular-ui/bootstrap/pull/1813