Prompt for password for Unknown network and nil buffer on connection

[farynaio]

I get this prompt in minibuffer when I run znc-all:

NickServ password for <username> on Unknown network (RET to cancel)

I always suppress that by pressing RET twice. After that I have one strange looking buffer named nil.

znc.el & ERC config I use:

(use-package erc
  :ensure nil
  :demand t
  :hook ((ercn-notify . my/erc-notify)
          (erc-send-pre . my/erc-preprocess))
  :custom
  (erc-port 6697)
  (erc-autoaway-message "I'm away (after %i seconds of idle-time)")
  (erc-nick-uniquifier "_")
  (erc-kill-server-buffer-on-quit t)
  (erc-kill-queries-on-quit t)
  (erc-track-showcount t)
  (erc-rename-buffers t)
  (erc-server-reconnect-timeout 3)
  (erc-track-exclude-types '("JOIN" "MODE" "NICK" "PART" "QUIT"
                              "324" "329" "332" "333" "353" "477"))
  (erc-hide-list '("JOIN" "PART" "QUIT"))
  (erc-lurker-hide-list '("JOIN" "PART" "QUIT"))
  (erc-autojoin-timing 'ident)
  (erc-user-mode "iR")
  (erc-header-line-format "%n on %t (%m) %o")
  (erc-join-buffer 'bury)
  (erc-lurker-threshold-time 43200)
  (erc-server-reconnect-attempts 5)
  :config
  (require 'erc-services)
  (require 'erc-join)

  (add-to-list 'erc-modules 'autojoin)
  (add-to-list 'erc-modules 'button)
  (add-to-list 'erc-modules 'completion)
  (add-to-list 'erc-modules 'fill)
  (add-to-list 'erc-modules 'irccontrols)
  (add-to-list 'erc-modules 'keep-place)
  (add-to-list 'erc-modules 'list)
  (add-to-list 'erc-modules 'match)
  (add-to-list 'erc-modules 'move-to-prompt)
  (add-to-list 'erc-modules 'netsplit)
  (add-to-list 'erc-modules 'networks)
  (add-to-list 'erc-modules 'notifications)
  (add-to-list 'erc-modules 'spelling)
  (add-to-list 'erc-modules 'noncommands)
  (add-to-list 'erc-modules 'readonly)
  (add-to-list 'erc-modules 'services)
  ;; (add-to-list 'erc-modules 'scrolltobottom)
  (add-to-list 'erc-modules 'ring)
  (add-to-list 'erc-modules 'stamp)
  (add-to-list 'erc-modules 'track)
  ;; (add-to-list 'erc-autojoin-channels-alist '(".*freenode.net" "#bitcoin" "#bitcoin-pricetalk"))

  (erc-services-mode 1)
  (erc-autojoin-mode 1)))

(use-package znc
:custom 
(setq
znc-servers '(("999.999.999" 55555 t
                      ((freenode "zncadmin" "password"))))))

Any ideas how to stop this prompt from popping up?
Is this nil buffer on purpose or it shouldn't be created? If it shouldn't how can I stop him for creating?

---

EDIT: I did some more investigations on the topic.

Even if I connect via regular ERC interface, the buffer nil is created, so it's probably how it is. But it would be great to have better name for it other than nil.

In regards to prompt in minibuffer I believe this is because freenode has many different servers and I don't have specified user/password for any of them in particular - just chat.freenode.org. But it would be great to do something about it as well, so this doesn't popup on start.