Fix stupid behaviour of relaybot plugin

Fixes issue 4257

Change-Id: Ic091c1bb415f37742f2ba74b1b371498c18b7be8
Reviewed-on: http://gerrit.dmdirc.com/1372
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Gregory Holmes <greg@dmdirc.com>

src/com/dmdirc/addons/relaybot/RelayCallbackManager.java

 
             // Clear my map of callbacks
             @SuppressWarnings("unchecked")
-            final Map<Class<? extends CallbackInterface>, CallbackObject> myCallbackHash = (Map<Class<? extends CallbackInterface>, CallbackObject>) cbField.get(this);
+            final Map<Class<? extends CallbackInterface>, CallbackObject> myCallbackHash = (Map<Class<? extends CallbackInterface>, CallbackObject>) cbField.get(cbm);
             myCallbackHash.clear();
 
             // Now add them all to the new cbm.