Fixes issue 3826: Colour chooser dialog should position itself before being made visible rather than appearing, then jumping

Change-Id: I90e1b51868dc35e332f680f6448f4ce500c8c2d7
Reviewed-on: http://gerrit.dmdirc.com/944
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Shane Mc Cormack <shane@dmdirc.com>

src/com/dmdirc/addons/ui_swing/dialogs/StandardDialog.java

@@ -118,6 +118,7 @@ public class StandardDialog extends JDialog {
                 executeAction(getCancelButton());
             }
         });
+        centreOnOwner();
         pack();
         centreOnOwner();
         setVisible(false);