Sync when adding and removing windows from the tree fixes issue 3645

Change-Id: Ibac7aac7b5f24a30e89509533c8bf63654b98ff2
Reviewed-on: http://gerrit.dmdirc.com/693
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Shane Mc Cormack <shane@dmdirc.com>

src/com/dmdirc/addons/ui_swing/framemanager/tree/TreeFrameManager.java

     /** {@inheritDoc} */
     @Override
     public void delWindow(final FrameContainer window) {
-        UIUtilities.invokeLater(new Runnable() {
+        UIUtilities.invokeAndWait(new Runnable() {
 
             /** {@inheritDoc} */
             @Override
      */
     public void addWindow(final TreeViewNode parent,
             final FrameContainer window) {
-        UIUtilities.invokeLater(new Runnable() {
+        UIUtilities.invokeAndWait(new Runnable() {
 
             /** {@inheritDoc} */
             @Override