Halfslab textures missing on 1.15.2

[terrarier2111]

Every other texture (except skulls and some other oddities) are present but it seems like halfslabs aren't present in any way shape or form, at least on the texture side of things, but if you walk on them their behavior is completely normal.

[iceiix]

Half slabs have changed their representation a few times over different protocol versions, to check https://github.com/iceiix/stevenarella/blob/master/blocks/src/lib.rs#L1275