Visual Bugs fixed

Hey everybody,

this update fixes a few visual bugs regarding background images and the cursor not showing properly in nodes. Also another bug was fixed with classes.

Changelog:

• v1.3.7
  • fixed a bug when using the class change core by Yanfly together with no actor based skill tree.
  • fixed a bug visual in the node confirm window that prevented the window from updating the cursor properly.
  • fixed a bug when switching from a tree with a background image to a tree with no background image. The old background image will now disappear properly.
  • fixed multiple bugs with the preloading of background images. All background images should now display when first selecting a tree.