Fix NPE in FD notifications plugin.

We had two instances of the FDManager around - one for the command and
once owned by the plugin. The command's instance was never loaded so
had no icon.

Change-Id: I525781a1ede263cbb0ee27f4fb0114dcded2245a
Fixes-Issue: CLIENT-471
Reviewed-on: http://gerrit.dmdirc.com/3231
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

src/com/dmdirc/addons/freedesktop_notifications/FDManager.java

@@ -38,9 +38,11 @@ import java.io.IOException;
 import java.util.ArrayList;
 
 import javax.inject.Inject;
+import javax.inject.Singleton;
 
 import org.apache.commons.lang.StringEscapeUtils;
 
+@Singleton
 public class FDManager implements ConfigChangeListener {
 
     /** Global configuration. */