Unable to have gas price of 0

Some dev networks allows gas price of 0 but when I try it here, I get

  File .../ledger-eth-lib/ledgereth/transactions.py", line 217, in create_transaction
    raise ValueError("gas_price or max_fee_per_gas must be provided")
ValueError: gas_price or max_fee_per_gas must be provided

The code is:

    # we need a gas price for a valid transaction
    if not gas_price and not max_fee_per_gas:
        raise ValueError("gas_price or max_fee_per_gas must be provided")

it probably should be

    # we need a gas price for a valid transaction
    if gas_price is None and max_fee_per_gas is None:
        raise ValueError("gas_price or max_fee_per_gas must be provided")

I have verified this fixes is my issue

I had no idea 0 gas price was valid. Good to know, thanks.

Making this change has some other implications as well. The defaults are hinky, then since they're all 0:

ledger-eth-lib/ledgereth/transactions.py

Lines 159 to 161 in 0b15b55

    
           gas_price: int = 0, 
        
           max_priority_fee_per_gas: int = 0, 
        
           max_fee_per_gas: int = 0,

Maybe gas_price should default to None and the others as 0 but in create_transaction() that would mean it would fallback to a type 0 transaction:

ledger-eth-lib/ledgereth/transactions.py

Line 220 in 0b15b55

if max_fee_per_gas:

Probably want to default them all to None then and then do some shitty logic checking for access lists to make sure it's not a type 1 tx before setting a default gas price or max fee. Or just use defaults at object instantiation...

Thinking about it a bit, if gas_price and max_fee_per_gas is zero, a type 0 tx would be just fine anyway. We should just remove that check, then. EZ

	gas_price: int = 0,
	max_priority_fee_per_gas: int = 0,
	max_fee_per_gas: int = 0,