New static method to return default card image

This will be used in deck import card preview (default state)

Signed-off-by: leriomaggio <valeriomaggio@gmail.com>

forge-gui-desktop/src/main/java/forge/ImageCache.java

@@ -397,4 +397,6 @@ public class ImageCache {
     public static boolean isDefaultImage(BufferedImage image) {
         return _defaultImage.equals(image);
     }
+
+    public static BufferedImage getDefaultImage() { return _defaultImage; }
 }