block proposals with invalid transactions lead to 0-tx-Blocks

[SurfingNerd]

If there are transactions that transfer more funds than the account has - the transaction is not processed because there is not enough balance.
So far so good.

The problem is, that hbbft see's the transaction as valid, and want's to start a block with it.
But the transaction can't get included, since it is not valid.
One Block later, the transaction is still here, and the loop starts again.
This loop generates an empty block all 5 seconds.

example:
Before Block 77568 we had a 0-tx block every 5 (~ min block time) seconds.
this could be solved by funding one account that had not enough funds to execute a transaction:
http://explorer.uniq.diamonds/blocks/77568
One block later, other transactions made by this account were included as well.
http://explorer.uniq.diamonds/blocks/77569.

Then the blockchain proceeded as normal.

[SurfingNerd]

verify claim: high nonce transactions (Transactions with missing nonce, are kept in the main pool queue.pool)
settings.nonce_cap EIP 168 has influence if those transactions make it into the pending pool.

[SurfingNerd]

propably we just need to take the pending transactions directly from the queue,
instead of client.queued_transactions() because those
Get a list of all transactions in the pool (some of them might not be ready for inclusion yet).

Here is a code snippet:

let queue_txs: Vec<Arc<_>> = self.transaction_queue.pending(
    client.clone(),
    pool::PendingSettings {
        block_number: chain_info.best_block_number,
        current_timestamp: chain_info.best_block_timestamp,
        nonce_cap,
        max_len: max_transactions.saturating_sub(engine_txs.len()),
        ordering: miner::PendingOrdering::Priority,
    },
);