There is an empty recipe for gray dye. Not sure which mod is causing this, but it is realy annoying in the ME System Crafting Terminal.

Fixed in pack v2.8
BYG creates a byg:gray_dye tag that has nothing in it, aka null
it then creates a recipe for minecraft:gray_dye using tag byg:gray_dye to make it, since the tag byg:gray_dye is null the recipe is nothing in the crafting grid to produce gray dye.
bde5658

I can verify that it's still an issue.