`hGetExactlyAt` found eof before reading

## Version
- released 1.25.1 cardano-node
- macos Big Sur
## How to reproduce

```
$ git clone https://github.com/yihuang/cardano-devnet
$ cd cardano-devnet
$ ./serve.sh
...
```

Only happened once, I can't reproduce it.

## Error message
```
[MacBook-:cardano.node.Forge:Info:41] [2021-02-28 07:49:10.80 UTC] fromList [("credentials",String "Shelley_Shelley"),("val",Object (fromList [("kind",String "TraceNodeNotLeader"),("slot",Number 124.0)]))]
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:10.80 UTC] fromList []
[MacBook-:cardano.node.LeadershipCheck:Info:41] [2021-02-28 07:49:11.00 UTC] {"credentials":"Shelley_Shelley","kind":"TraceStartLeadershipCheck","delegMapSize":0,"slot":125,"chainDensity":7.1428575e-2,"utxoSize":1}
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.Forge:Info:41] [2021-02-28 07:49:11.00 UTC] fromList [("credentials",String "Shelley_Shelley"),("val",Object (fromList [("kind",String "TraceNodeIsLeader"),("slot",Number 125.0)]))]
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.Forge:Info:41] [2021-02-28 07:49:11.00 UTC] fromList [("credentials",String "Shelley_Shelley"),("val",Object (fromList [("kind",String "TraceForgedBlock"),("slot",Number 125.0)]))]
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList [("kind",String "OutcomeTraceForgeEvent"),("difftime",Number 8.47e8),("slot",Number 125.0),("mempoolbytes",Number 0.0),("mempoolnumtx",Number 0.0)]
[MacBook-:cardano.node.ChainDB:Notice:31] [2021-02-28 07:49:11.00 UTC] Chain extended, new tip: 81322a986cdfc5257ecf9dc86fd0651a753f36ebc1e3913e59b9dc37dd74517f at slot 125
[MacBook-:cardano.node:Info:41] [2021-02-28 07:49:11.00 UTC] fromList [("time(ps)",Number 2.065820915469e18),("kind",String "MeasureTxsTimeStop"),("slot",Number 125.0)]
[MacBook-:cardano.node.Forge:Info:41] [2021-02-28 07:49:11.00 UTC] fromList [("credentials",String "Shelley_Shelley"),("val",Object (fromList [("blockSize",Number 1008.0),("kind",String "TraceAdoptedBlock"),("blockHash",String "81322a986cdfc5257ecf9dc86fd0651a753f36ebc1e3913e59b9dc37dd74517f"),("slot",Number 125.0)]))]
[MacBook-:cardano.node.ForgeTime:Info:41] [2021-02-28 07:49:11.00 UTC] fromList []
[MacBook-:cardano.node.ChainDB:Notice:5] [2021-02-28 07:49:11.00 UTC] before next, messages elided = 2065820915402999
[MacBook-:cardano.node.ChainDB:Notice:5] [2021-02-28 07:49:11.00 UTC] Chain extended, new tip: 81322a986cdfc5257ecf9dc86fd0651a753f36ebc1e3913e59b9dc37dd74517f at slot 125

Shutting down..
ApiMisuse (ClosedDBError (Just (UnexpectedFailure (FileSystemError (FsError {fsErrorType = FsReachedEOF, fsErrorPath = /Users/huangyi/src/cardano-devnet/data/db/volatile/blocks-0.dat, fsErrorString = "hGetExactlyAt found eof before reading 967 bytes", fsErrorNo = Nothing, fsErrorStack = CallStack (from HasCallStack):
prettyCallStack, called at src/Ouroboros/Consensus/Storage/FS/API.hs:212:31 in ouroboros-consensus-0.1.0.0-7N0TYprJv9lD4pOQ7LYImI:Ouroboros.Consensus.Storage.FS.API
hGetExactlyAt, called at src/Ouroboros/Consensus/Storage/VolatileDB/Impl.hs:285:11 in ouroboros-consensus-0.1.0.0-7N0TYprJv9lD4pOQ7LYImI:Ouroboros.Consensus.Storage.VolatileDB.Impl
getBlockComponentImpl, called at src/Ouroboros/Consensus/Storage/VolatileDB/Impl.hs:221:35 in ouroboros-consensus-0.1.0.0-7N0TYprJv9lD4pOQ7LYImI:Ouroboros.Consensus.Storage.VolatileDB.Impl
getBlockComponent, called at src/Ouroboros/Consensus/Storage/VolatileDB/API.hs:61:7 in ouroboros-consensus-0.1.0.0-7N0TYprJv9lD4pOQ7LYImI:Ouroboros.Consensus.Storage.VolatileDB.API, fsLimitation = False})))))

cardano-node: VolatileDB incorrectly used, indicative of a bug./data/node.socket
```