Tidy up nick change handling.

It doesn't make sense to have a public method in Connection to
muddle around with how queries are tracked, nor for queries to
tell servers when they change (creating a dependency loop).

Instead, have the ServerEventHandler tell Server.

src/main/java/com/dmdirc/Query.java

 import com.dmdirc.parser.interfaces.Parser;
 import com.dmdirc.ui.core.components.WindowComponent;
 import com.dmdirc.ui.messages.BackBufferFactory;
+import net.engio.mbassy.listener.Handler;
 
-import java.awt.Toolkit;
+import java.awt.*;
 import java.util.Arrays;
 import java.util.Optional;
 
-import net.engio.mbassy.listener.Handler;
-
 /**
  * The Query class represents the client's view of a query with another user. It handles callbacks
  * for query events from the parser, maintains the corresponding QueryWindow, and handles user input
         final ClientInfo client = event.getClient();
         final String oldNick = event.getOldNick();
         if (client.getNickname().equals(getNickname())) {
-            connection.updateQuery(this, oldNick, client.getNickname());
-
             getEventBus().publish(new QueryNickChangeEvent(this, oldNick, client.getNickname()));
             updateTitle();
 

src/main/java/com/dmdirc/Server.java

 import javax.annotation.Nullable;
 import javax.net.ssl.SSLException;
 
+import net.engio.mbassy.listener.Handler;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import net.engio.mbassy.listener.Handler;
-
 import static com.dmdirc.util.LogUtils.APP_ERROR;
 import static com.google.common.base.Preconditions.checkNotNull;
 
     private final ServerEventHandler eventHandler;
     /** Our ignore list. */
     private final IgnoreList ignoreList = new IgnoreList();
-    /** Our string convertor. */
+    /** Our string converter. */
     private StringConverter converter = new DefaultStringConverter();
     /** ParserFactory we use for creating parsers. */
     private final ParserFactory parserFactory;
         return queries.get(lnick);
     }
 
-    @Override
-    public void updateQuery(final Query query, final String oldNick, final String newNick) {
-        windowModel.getInputModel().get().getTabCompleter()
-                .removeEntry(TabCompletionType.QUERY_NICK, oldNick);
-        windowModel.getInputModel().get().getTabCompleter()
-                .addEntry(TabCompletionType.QUERY_NICK, newNick);
+    /**
+     * Updates tab completer and queries after a user changes their nickname.
+     *
+     * @param client The client that changed nickname
+     * @param oldNick The old nickname they used.
+     */
+    void handleNickChange(final ClientInfo client, final String oldNick) {
+        if (queries.containsKey(converter.toLowerCase(oldNick))) {
+            windowModel.getInputModel().get().getTabCompleter()
+                    .removeEntry(TabCompletionType.QUERY_NICK, oldNick);
+            windowModel.getInputModel().get().getTabCompleter()
+                    .addEntry(TabCompletionType.QUERY_NICK, client.getNickname());
 
-        queries.put(converter.toLowerCase(newNick), query);
-        queries.remove(converter.toLowerCase(oldNick));
+            queries.put(
+                    converter.toLowerCase(client.getNickname()),
+                    queries.remove(converter.toLowerCase(oldNick)));
+        }
     }
 
     @Override
      * {@code orElse} value.
      */
     private <T> T withParserReadLock(
-            final Function<? super Parser, ? extends T> func,
+            final Function<Parser, T> func,
             final T orElse) {
         try {
             parserLock.readLock().lock();

src/main/java/com/dmdirc/ServerEventHandler.java

 import com.dmdirc.parser.events.WallopEvent;
 import com.dmdirc.parser.events.WalluserEvent;
 import com.dmdirc.ui.StatusMessage;
+import net.engio.mbassy.listener.Handler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
+import javax.annotation.Nonnull;
 import java.util.List;
 import java.util.Optional;
 import java.util.Random;
 
-import javax.annotation.Nonnull;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import net.engio.mbassy.listener.Handler;
-
 import static com.dmdirc.util.LogUtils.APP_ERROR;
 import static com.dmdirc.util.LogUtils.USER_ERROR;
 
                     event.getOldNick(), event.getClient().getNickname()));
             owner.updateTitle();
         }
+
+        owner.handleNickChange(event.getClient(), event.getOldNick());
     }
 
     @Handler

src/main/java/com/dmdirc/interfaces/Connection.java

 import com.dmdirc.parser.common.IgnoreList;
 import com.dmdirc.parser.interfaces.Parser;
 
+import javax.annotation.Nonnull;
 import java.net.URI;
 import java.util.Collection;
 import java.util.Optional;
 
-import javax.annotation.Nonnull;
-
 /**
  * Represents an abstract connection to a remote chat system.
  */
      */
     void updateIgnoreList();
 
-    /**
-     * Updates the state of this server following a nick change of someone that the user has a query
-     * open with. Namely, this updates the tabcompleter with the new name, and ensures that the
-     * <code>queries</code> map uses the correct nickname.
-     *
-     * @param query   The query object being updated
-     * @param oldNick The old nickname of the user
-     * @param newNick The new nickname of the user
-     *
-     * @since 0.6.4
-     */
-    void updateQuery(final Query query, final String oldNick, final String newNick);
-
     /**
      * Updates the name and title of this window.
      */