* both 'to' and 'from' are either Null or Hash160, there is no other
possibility for valid NEP-17. So returning util.Uint160{} in case of
parsing error is wrong.
* but this is what allowed burns/mints to work at the expense of error
allocation inside of util.Uint160DecodeBytesBE()
* Uint160 can technically fit into regular VM integer, so even though it'd be
quite surprising to see it there, TryBytes() is more correct (and easier!)
to use
* same thing with `amount`, we have `TryInteger()` that easily covers all
possible cases and does appropriate error checking inside
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