Default texture minecraft:item/leather_helmet_overlay causing mipmap to drop from 4 to 0

Error message in the log file:

[Server-Worker-6/WARN]: Texture minecraft:item/leather_helmet_overlay with size 1x1 limits mip level from 4 to 0
[Server-Worker-6/WARN]: minecraft:textures/atlas/blocks.png: dropping miplevel from 4 to 0, because of minimum power of two: 1