Buttons should be disabled if the actions can't be performed.

**Is your feature request related to a problem? Please describe.**
The "modify", "delete" and "save" button can be clicked. This can cause some weird scenario's, like having an empty modify modal.

**Describe the solution you'd like**
Make it possible to disable buttons. They should be grayed out.

**Describe alternatives you've considered**
Go over the scenarios and fix them.