Exception at tick 6311383: Error while running event Achiever::on_resource_depleted (ID 25)
Achiever/control.lua:67: attempt to index field '?' (a nil value)

The cause is that the entities array returned by find_entities_filtered() is not nil, but empty.

While fixing the code for my game, I noticed that the logic used was flawed. You check for entities of type mining drill at the same position were the resource patch was located, while electric mining drills have a mining area larger than their entity. This is why the error happened, the patch was located on the outside edge of a mining drill, but not under the mining drill.

The ideal logic to trigger the achievement should be: enable achievement for all the players of the force that placed the miner that depleted an ore patch. Unfortunately this logic can't be implemented as there is no information in the event which entity caused the depletion, it can be even a player mining with a pickaxe.

A close enough logic, that works in game would be to search for all the miners in an small enough area surrounding the depleted patch location, check the miners and see whether or not they could have targeted the patch, considering their placement and the mining area. For this to work even with modded mining drills, you have to check the runtime data of the drills in question. You can check the code of "https://mods.factorio.com/mods/mindmix/AutoDeconstruct" for a more complete implementation and inspire yourself.