fix bug Option::unwrap() on a None value

[Lihui-Gu]

The original code only checks whether start_of_indices is None, but it does not check whether end_of_indices is None. However, it still calls .unwrap() on end_of_indices later without verifying its validity. This leads to a potential panic when end_of_indices is actually None.

if start_of_indices.is_none() {
    return;
}

let start_of_indices = start_of_indices.unwrap(); // ✅ safe
let end_of_indices = end_of_indices.unwrap();     // ❌ if None，panic !!!

Code change:

match (start_of_indices, end_of_indices) {
    (Some(start), Some(end)) => {
        // safely use start, end
    }
    _ => return, 
}