pylint cleanup: initialise all attributes in __init__()

Reviewed-by: James Cameron <quozl@laptop.org>
Acked-by: Simon Schampijer <simon@laptop.org>
CC: Aleksey Lim <alsroot@member.fsf.org>

src/sugar/graphics/palettewindow.py

@@ -147,6 +147,7 @@ class PaletteWindow(gtk.Window):
         self._alignment = None
         self._up = False
         self._old_alloc = None
+        self._palette_state = None
 
         self._popup_anim = animator.Animator(.5, 10)
         self._popup_anim.add(_PopupAnimation(self))