#1 Predefined formats editable

[A.B.]

It is possible to edit predefined formats, which are expected to be never modified. In order to reproduce this behaviour do the following:

- Create a new custom format for a code snippet, disable the Block display
- Select the format in the Properties view, Edit and Delete button are enabled
- Change display type to Block
- new format disappears from list of formats, another format is selected
- Edit and Delete buttons are still enabled (and working), even if selected format is a predefined one