bug#23700: Patch to fix erc-kill-channel sending command to server when no connection

[Fran Litterio]

In the latest Emacs sources, function erc-default-target returns
nil when ERC is no longer connected to the server for the current
ERC buffer.  This can cause erc-kill-channel to try to send a
command to the disconnected server when a channel buffer is killed.
This patch fixes that.
--
Fran Litterio


diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 8501e2c..da5edf1 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -6735,9 +6735,10 @@ This function should be on `erc-kill-server-hook'."
 This function should be on `erc-kill-channel-hook'."
   (when (erc-server-process-alive)
     (let ((tgt (erc-default-target)))
-      (erc-server-send (format "PART %s :%s" tgt
-                               (funcall erc-part-reason nil))
-                       nil tgt))))
+      (if tgt
+         (erc-server-send (format "PART %s :%s" tgt
+                                  (funcall erc-part-reason nil))
+                          nil tgt)))))
 
 ;;; Dealing with `erc-parsed'