I'm not sure whether this counts as a bug fix request or a new feature request, so I'm giving it a new thread.
Currently, the editor does not allow for a lock with a requirement of 0 keys. I understand why having exactly 0 copies is banned - a door with 0 copies would immediately destroy itself - but I think locks with 0 key requirements would have a use. A positive 0 key lock might not spend any keys, but it would still require you to have at least 0 keys to open it, i.e. it would be a check to make sure the real part of your key count is nonnegative. I don't believe there's currently a way to do this with a single door, so this could have uses in puzzles. Likewise, a negative 0 key lock would check to make sure the real part of your key count is nonpositive, a positive 0i key lock would make sure the imaginary part of your key count is nonnegative, and a negative 0i key lock would make sure the imaginary part of your key count is nonpositive.
I could especially see these being useful with Gates. If you think of "can you pass this gate with positive, zero, or negative keys" as a three-bit question, with the order of the bits being positive, zero, negative, then a wall (just some tiles blocking the way, not a door or gate) is 000, an empty hallway is 111, a Blank gate is 010, a positive Blast gate (or a positive 1 gate) is 100, a negative Blast gate (or a negative 1 gate) is 001, and an All gate is 101. Including 0 locks would round this out nicely, as a positive 0 gate would be 110 and a negative 0 gate would be 011.
In conclusion, locks with a count of 0 could have uses, and so I am requesting that they be allowed.