From 2f5d47b1df0248a6fd14b65889e564859cf305c8 Mon Sep 17 00:00:00 2001
From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Sat, 14 Apr 2018 20:37:09 +0200
Subject: [PATCH] Ignore all-whitespace topics in erc

* lisp/erc/erc.el (erc-cmd-TOPIC): Ignore all-whitespace topics
(bug#25153).
---
 lisp/erc/erc.el | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 63228516be7..f1e21c9a96f 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -3693,8 +3693,10 @@ be displayed."
    ((string-match "^\\s-*\\([&#+!]\\S-+\\)\\s-\\(.*\\)$" topic)
     (let ((ch (match-string 1 topic))
           (topic (match-string 2 topic)))
-      (erc-log (format "cmd: TOPIC [%s]: %s" ch topic))
-      (erc-server-send (format "TOPIC %s :%s" ch topic) nil ch))
+      ;; Ignore all-whitespace topics.
+      (unless (equal (string-trim topic) "")
+	(erc-log (format "cmd: TOPIC [%s]: %s" ch topic))
+	(erc-server-send (format "TOPIC %s :%s" ch topic) nil ch)))
     t)
    ;; /topic #channel
    ((string-match "^\\s-*\\([&#+!]\\S-+\\)" topic)
-- 
2.39.5