Free topic array on channel deletion.

The topic array in the CHANNEL structure must be free()'d before the
channel itself becomes deleted.

src/ngircd/channel.c

@@ -1086,7 +1086,7 @@ Delete_Channel( CHANNEL *Chan )
 
 	Log( LOG_DEBUG, "Freed channel structure for \"%s\".", Chan->name );
 
-	/* free invite and ban lists */
+	array_free(&chan->topic);
 	Lists_Free(&chan->list_bans);
 	Lists_Free(&chan->list_invites);