HD Pack: Display bug with sprites with background priority

[mkwong98]

When playing with HD pack, the sprites are not visible if they have background priority and there is no custom background image being shown. For example in SMB, the mushroom power up is not visible when it is coming out of the question block. This problem is only present when HD pack is in use. This problem is not in version 0.9.9 but is in version 0.9.9.49 and 0.9.9.62 (I only have these versions) so I think this problem is introduced when adding the multiple backgrounds feature on May 9.