Fix window becoming unthemed when unfocused

Author: rsubtil

resources/default_theme.tres

@@ -791,5 +791,6 @@ VSlider/styles/grabber_area = SubResource("StyleBoxFlat_lt218")
 VSlider/styles/grabber_area_highlight = SubResource("StyleBoxFlat_id7ai")
 VSlider/styles/slider = SubResource("StyleBoxFlat_go4h4")
 Window/styles/embedded_border = SubResource("StyleBoxFlat_sfm0d")
+Window/styles/embedded_unfocused_border = SubResource("StyleBoxFlat_sfm0d")
 Window/styles/panel = SubResource("1662")
 WindowPanel/styles/panel = SubResource("StyleBoxFlat_e1x58")