Panicked while issuing assets with empty params

[yuyaogawa]

I get an error when issuing assets with empty params.

thread 'tokio-runtime-worker' panicked at 'called `Result::unwrap()` on an `Err` value: ParseIntError { kind: Empty }', src/wallet/issue/rgb20.rs:43:55
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'actix-rt|system:0|arbiter:0' panicked at 'called `Result::unwrap()` on an `Err` value: JoinError::Panic(Id(168), ...)', src/wallet/issue/rgb20.rs:48:14
thread 'actix-rt|system:0|arbiter:0' panicked at 'called `Result::unwrap()` on an `Err` value: PoisonError { .. }', src/wallet/issue/rgb20.rs:29:20
thread 'actix-rt|system:0|arbiter:0' panicked at 'called `Result::unwrap()` on an `Err` value: PoisonError { .. }', src/wallet/issue/rgb20.rs:29:20
thread 'actix-rt|system:0|arbiter:0' panicked at 'called `Result::unwrap()` on an `Err` value: PoisonError { .. }', src/wallet/issue/rgb20.rs:29:20