How to ignore characters that have not been successfully encoded?

[mzdk100]

My code is

let (text, _, _) = GBK.encode("abc‎");
dbg!(&text);

Output:

&text = [
    97,
    98,
    99,
    38,
    35,
    56,
    50,
    48,
    54,
    59,
]

The encoded text is actually "abc‎". How do I discard "‎"?