No response if user tries to add new component to channel with deleted preview in runtime.

Scenario:

1. Open channel.
2. In console delete preview for that channel.
3. Try to add some component to some container for opened channel.

Expected: Toast message about problem. 

Current result: There is no any reaction from cms and it's not possible to add component.

Note that on that state almost entire functionality of channel editor doesn't work but at the same time there is no clear system response and UI notification about problem