Some checking in checkUserOnChannel. Probably fixes issue 3473.

Change-Id: I8e580edc2e37d60524673bab073914bb4f0f3a1f
Reviewed-on: http://gerrit.dmdirc.com/437
Reviewed-by: Gregory Holmes <greboid@dmdirc.com>
Tested-by: Gregory Holmes <greboid@dmdirc.com>

src/com/dmdirc/addons/parser_twitter/Debug.java

@@ -36,6 +36,8 @@ enum Debug {
     dataIn,
     /** Debug information for data output. */
     dataOut,
+    /** Error with internal state. */
+    stateError,
     /** General error info from the twitter parser. */
     twitterError,
     /** More debuggy error info from the twitter parser. */

src/com/dmdirc/addons/parser_twitter/Twitter.java

@@ -817,6 +817,11 @@ public class Twitter implements Parser, TwitterErrorHandler, TwitterRawHandler,
     private boolean checkUserOnChannel(final TwitterUser user) {
         final TwitterChannelInfo channel = (TwitterChannelInfo) this.getChannel(mainChannelName);
 
+	if (channel == null) {
+		doDebug(Debug.stateError, "Tried to check user (" + user.getScreenName() + "), but channel is null.");
+		return false;
+	}
+
         if (channel.getChannelClient(user.getScreenName()) == null) {
             final TwitterClientInfo ci = new TwitterClientInfo(user.getScreenName(), this);
             clients.put(ci.getNickname().toLowerCase(), ci);