fix(blockchair): handle zero balance addresses edge case

[tomiiide]

What was done?

The problem

When an address has a zero balance, they blockchair API returns an empty data object causing the getBalance to return an error , which in turn breaks getUTXO

Address with balance

Zero Balance address

The fix

To fix this, 0 is returned in getBalance when the data object is empty, and in getUTXOs a default value of balance is set to 0.

[chybisov]

Can you please provide some context - if we return 0n here now, are we still going to fallback to other providers to try fetch the price when it's not available in blockchair? We need to add tests for our retry logic.

[tomiiide]

There is a check above that throws an error when the req status is not a 200, or when blockchair returns an error object. So, if blockchair fails, the fallback would still happen.

This is for an edge case that happens on blockchair when the data object is empty, and it happens when the address is non existent or has a 0 address.

[tomiiide]

Though returning 0n did not break fallback logic. I've reverted to throwing an error as it is more accurate.

The error thrown by getBalance would be caught and thrown by getUTXOs which would trigger the fallback logic.

I also added test for this edge case.

@chybisov