Fix /topic using wrong formatter

Fixes issue 1613

git-svn-id: http://svn.dmdirc.com/trunk@4539 00569f92-eb28-0410-84fd-f71c24880f

src/com/dmdirc/commandparser/commands/channel/ShowTopic.java

             if (cChannel.getTopic().isEmpty()) {
                 sendLine(origin, isSilent, "channelNoTopic", cChannel);
             } else {
-                sendLine(origin, isSilent, "channelJoinTopic", cChannel.getTopic(),
+                sendLine(origin, isSilent, "channelTopicDiscovered", cChannel.getTopic(),
                         cChannel.getTopicUser(), 1000 * cChannel.getTopicTime(), cChannel);
             }
         } else {