I have performed some changes on my storyboard file and deleted a bar button. Before deleting, I removed all the connections in both storyboards for both screens. 

Next, I deleted all the code, connected with this button. 

Now I'm getting an error on startup:

```
*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason:
'[<TTPDepartmentViewController 0xe805bd0> setValue:forUndefinedKey:]: 
this class is not key value coding-compliant for the key nextButton.'

```

I've checked for this `nextButton` all over the source code of storyboards and all. No sign, no connections, still this error bumps out. More, I've reseted the simulation. What can I do? 

UPD: I totally removed the problematic (as I thought) storyboard and the problem still appears, even that other storyboards do not contain these views with this key at all.

UPD2: ![unleashedprop](https://i.stack.imgur.com/r2p0w.png)

As you can see the connection thing is not filled, so there should be no connection. When I uncomment this line it builds and runs, though it is not obviously used at all.