I actually recently got the exact same bug, for crafting a bow for my magic mod.
The recipe is as follows:
.Enchant a Bow. "Longbow" [effort:0] [phys:hand] *WEATHERLORE* /1/ |2| %20%
{[NEARBY_TILE:mountain]} +'Pray at the Shrine'
{Fire} +'Sacrificial Fire'
{Weapon Enchanting Rune} (1) [remove] [noquality]
{*Bow} (1) [remove] +'Northern, Hunting, or Longbow.'
[NAME:Enchanted Bow]
[POINT_ATTACK:9]
It creates an enchanted bow with no string, which can then be strung normally.
Normally I wouldn't report bugs that only occur with a mod, but it told me to report!
EDIT: This is 3.72 patch 1 on Windows