This will return `None` if `get_consumption()` returns zero. Is that the intended result?

Notice the subtle difference from the logic in `resupply_quantity_needed`:

| Function | condition | result |
| ------------ | ------------ | ------- |
| `resupply_quantity_needed` | `get_consumption() is None` | `None` |
| `lambda s: ...` | `not get_consumption()` | `None` |