Insert actual emptyRoot where not applicable

[georgi-l95]

Problem

Currentlty in our implementation of Block, where we don't know the actual trie root, we are ruturning some random value or 0x. This is not correct as some tools might need this information or at least require this to be in the correct format.

Solution

We can easly implement ethereum tree library, like this https://www.npmjs.com/package/@ethereumjs/trie. Using it we can define new empty trie and either populate or return actual emtpy root.