panic when the number of keys is 1

[coocood]

The following code panics with message attempt to subtract with overflow

BinaryFuse8::try_from(&vec![1u64])

[ayazhafiz]

Happy to take a patch for this.

[coocood]

It's caused by capacity is zero, then (capacity + segment_length - 1) / segment_length is zero, less than (arity - 1)

            let capacity: u32 = if size > 1 {
                (size as f64 * size_factor).round() as u32
            } else { 0 };
            let init_segment_count = (capacity + segment_length - 1) / segment_length - (arity - 1);

Any suggestion on how to fix it? Thank you.