Question on `era` file structure
We are currently implementing support for `era` files in Javascript within the [`ethereumjs-monorepo`](https://github.com/ethereumjs/ethereumjs-monorepo/tree/master/packages/era) and I have a question about the encoding of empty slots.  When we deserialize [this era file](https://mainnet.era.nimbus.team/mainnet-00001-40cf2f3c.era) there are slots where there is no block (presumably a missed slot) and instead there is an entry that decodes as 
`{ type: [0x65, 0x32], data: [] }` which looks like the `VERSION` entry type specified in the e2store documentation.  

The language around the [structure of the era file](https://github.com/status-im/nimbus-eth2/blob/613f4a9a50c9c4bd8568844eaffb3ac15d067e56/docs/e2store.md#structure) just says that "missed slots are skipped".  Is Nimbus coding this "skipped slot" as a VERSION entry or am I misunderstanding something about the structure of the file?
