Undyed shulker boxes show up as white on maps

On maps, shulker boxes that aren't dyed show up as white on maps, even though they are still purple in color. On the top is the undyed boxes, and on the bottom is dyed purple boxes.

Steps to Reproduce:

1. Place multiple undyed shulker boxes
2. Open a map

Observed Results:
The shulker boxes show up as white on the map.

Expected Results:
The shulker boxes should show up as purple.