Endermen holding signs do not appear to be holding anything

Relates to MC-206451

When holding most blocks, they render held by the enderman just fine. However, this does not apply to signs, likely due to their tile entity rendering.

I would STRONGLY recommend that signs change to using block models for rendering to fix this (for everything but the text), as there is no benefit to using entity rendering for them and changing over to block models allows for further customization and also fixes several other bugs signs have due to using entity rendering.

To reproduce:

1. /summon minecraft:enderman ~ ~ ~ {carriedBlockState:{Name:oak_sign}}

2. Note that it appears to be holding literally nothing
3. Kill it and note the drops