This is something we could fix up later, but, I feel like it might be more friendly if `overwrite_input=True` and the input is not an array to just silently carry on regardless? No-one uses an option like `overwrite_input` because they *insist* that the input be overwritten; it's a kind of "I don't care about this object, so feel free to use it if you want" option. (Notice that *not* overwriting the input is totally compatible with `overwrite_input`'s guarantees, since it makes none.)