Describe the bug
Blutgang will sometimes respond with {"id":1,"jsonrpc":"2.0","result":null} when returning results from the cache.

To Reproduce
Steps to reproduce the behavior:

1. Make a querry Blutgang is able to cache and respond with
2. Sometimes you will get an invalid response

Expected behavior
Blutgang should never cache invalid responses like {"id":1,"jsonrpc":"2.0","result":null}