Panic when constructing a dynamic transaction with invalid arguments

[AlexD10S]

I encountered a panic! in the subxt library when attempting to construct a dynamic transaction call_data with invalid arguments.
The issue occurs in this specific line of codehttps://github.com/paritytech/subxt/blob/master/core/src/tx/payload.rs#L186

Error output:

The fields are valid types from the metadata, qed;: Error { context: Context { path: [Location { inner: Index(0) }] }, kind: WrongShape { actual: Number, expected_id: "13" } }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Steps to Reproduce

let arg = scale_value::stringify::from_str_custom()
				.add_custom_parser(custom_parsers::parse_hex)
				.add_custom_parser(custom_parsers::parse_ss58)
				.parse("123")
				.0?;
subxt::dynamic::tx("System", "remark", parsed_args);
let call_data = tx.encode_call_data(&client.metadata());

I should ensure proper validation of the requested arguments before constructing the transaction. However, if the provided arguments are invalid, it would be ideal for the encode_call_data function to throw a meaningful error instead of causing a panic.

[niklasad1]

I should ensure proper validation of the requested arguments before constructing the transaction. However, if the provided arguments are invalid, it would be ideal for the encode_call_data function to throw a meaningful error instead of causing a panic.

Yes agree, it should be an easy fix.