Villages generate without villagers

there were no villagers, no cats, no iron golum, no animals in the pens and no animals even Around the villages. just complete emptiness in the area.

I have had this happen before and came up with the following explanations.

Mobspawning Gamerule

One possibility is that you turned off the mobspawning gamerule temporarily at some point, and the village was generated while it was off.

Villagers aren't like other mobs (animals and monsters): They don't spawn dynamically when you approach their village, because that would mean you'd have a different set of villagers every time you come back to the village. Instead, villagers need to be persistent, and that means they're actually part of the village. They spawn during village generation, and that's the only time they can spawn.

But villagers are nevertheless subject to the mobspawning gamerule, just like other mobs. So if the gamerule is turned off when a village generates, it will generate with no villagers in it, and none will spawn in it at a later time, either.

You might think this is unlikely, because while you did turn off mob spawning at some point, you weren't near the village at the time and you turned it back on before you went there. Unfortunately, you can't rely on this analysis, because villages can generate at times you didn't expect, and can even generate without you being able to see them. (Bear with me; this will take a bit of explaining.)

Villages generate during chunk generation, after the chunk's terrain has been generated. Chunks generate when you first look at them. (This is an oversimplification, but I'm pretty sure it's how the great majority of chunks get generated.) For chunks out near the limits of your render distance, it's very common for intervening terrain to obscure your view of their ground level, but they often have tall trees, mountains, or floating islands that stick up high enough to be visible, so the chunk will get generated anyway. If such a chunk contains a village, the village will be generated even though you can't see any part of it and aren't near it. Thus, all it would take to get an unpopulated village is to turn off mob spawning and look around a bit in an area you haven't completely explored. And if you start walking around, the chance of generating an unpopulated village grows rapidly higher.

Aborted Village Generation

On rare occasions, the game will start to generate a village but not complete it. I'm not sure what causes this—it might be a bug, in fact—but I have definitely seen examples of it. For instance, I once found a village that contained only one complete building and part of another with a bit of grass path between them. My best guess in this case is that the village anchor point (the center point around which it's generated) was in a chunk that hadn't been generated, but that the village extended into a chunk that had been generated earlier, before the Village & Pillage Update. (The update changed the calculation of which chunks contain villages, so when the extension chunk was generated there wasn't supposed to be a village there, and it was generated without one.)

I can imagine that when a village is being generated that extends into an adjacent chunk, and the game discovers that that chunk already exists, it might abort generating the rest of the village on the theory that the second chunk already contains its part of the village. While this logic is flawed in the case of a pre-V&P world, you can't really do better than that if you want the kind of changes V&P introduced, so Mojang would have left it as a "Won't Fix"-type glitch. But since villager spawning happens after village generation, it's likely that aborting village generation cancels the spawning, leaving the village unpopulated.

The telltale symptom for this scenario would be an obvious discontinuity in the village, like my partial house, but depending on where the chunk boundary happens to lie, there might not be any clues that such a thing has happened. That is, the village might look perfectly normal, just a little smaller than usual. And of course, it would be unpopulated.