When a player enters a new world, so they have not killed a villager, goes to a village, and only kills generic villagers, the village golem will attack and have the attack animation triggered, but will cause no damage to the player.

I've done multiple tests, with different amounts of generic villagers, and it seems if there are any villagers who are not generic, the golem will cause damage. Also, if the player has already angered a golem the bug will not occur.

All tests of only generic villagers using /summon cause the bug.
Haven't found a village with enough generic villagers and a golem to do a natural test.

Recreation:
/gamemode 1
/locate Village returns -235 ? 635 (not actual values)
/tp -235 ~ 635
/give @p minecraft:diamond_sword 1 0

{ench:[id:16,lvl:150]}

/summon minecraft:villager_golem
/summon minecraft:villager

{Profession:5}

multiple times, crash report attached.
/summon minecraft:villager

{Profession:5, Age:-6000}

multiple times
Kill all summoned villagers.
/gamemode 0