Properly handle multiline topics

fix #3254

src/bridge/bridge.cpp

@@ -684,9 +684,12 @@ void Bridge::send_irc_kick(const Iid& iid, const std::string& target, const std:
   this->add_waiting_irc(std::move(cb));
 }
 
-void Bridge::set_channel_topic(const Iid& iid, const std::string& subject)
+void Bridge::set_channel_topic(const Iid& iid, std::string subject)
 {
   IrcClient* irc = this->get_irc_client(iid.get_server());
+  std::string::size_type pos{0};
+  while ((pos = subject.find('\n', pos)) != std::string::npos)
+    subject[pos] = ' ';
   irc->send_topic_command(iid.get_local(), subject);
 }
 

src/bridge/bridge.hpp

@@ -83,7 +83,7 @@ public:
   void send_irc_nick_change(const Iid& iid, const std::string& new_nick, const std::string& requesting_resource);
   void send_irc_kick(const Iid& iid, const std::string& target, const std::string& reason,
                      const std::string& iq_id, const std::string& to_jid);
-  void set_channel_topic(const Iid& iid, const std::string& subject);
+  void set_channel_topic(const Iid& iid, std::string subject);
   void send_xmpp_version_to_irc(const Iid& iid, const std::string& name, const std::string& version,
                                 const std::string& os);
   void send_irc_ping_result(const Iid& iid, const std::string& id);