omni: add EmptyOverlay

see README for more information

Change-Id: If1e13145e5e447a37ab119e7583bb7ad46e88a84
diff --git a/themes/overlays/Android.mk b/themes/overlays/Android.mk
index 0eb3c82..e7c0e5e 100644
--- a/themes/overlays/Android.mk
+++ b/themes/overlays/Android.mk
@@ -26,7 +26,8 @@
 	PrimaryColorDeepBlueOverlay \
 	AccentColorRedDevilOverlay \
 	FontLatoSourceOverlay \
-	FontMuliSourceOverlay	
+	FontMuliSourceOverlay \
+	EmptyOverlay
 
 include $(BUILD_PHONY_PACKAGE)
 include $(CLEAR_VARS)