Can't exit NSSearchField after inserted text and cleared it

I added an NSSearchField to my NSViewController, which is the main controller of my outline view. Now it implements next classes:

class MainCatalogNSViewController: NSViewController, NSOutlineViewDelegate, NSOutlineViewDataSource, NSSearchFieldDelegate {
    override func viewDidLoad() {
        super.viewDidLoad()
        searchField.delegate = self
    }
}

The search field works well without any issues until I set a delegate as above. Once it's set, I can't exit it if was edited and cleared.

Could you please explain to me why this happens? Can this issue be related to outline view? I used the NSSearchField before, and it always worked well.

The root of the issue was the next method, declared in the NSViewController, which prevents saving of the empty cells in the outline view:

func control(_ control: NSControl, textShouldEndEditing fieldEditor: NSText) -> Bool {
    // don't allow empty node names
    return !(fieldEditor.string.isEmpty ?? true)
}

And now it handles the NSSearchField events in this case, instead of outline view table cells editing.