Bug: IndexMap fails to insert more than u16::MAX keys.

I ran into this bug when inserting a lot of keys in an IndexMap, and it turns out that when my keys are bigger than an u16 they are not inserted properly. Here is a minimal reproducible code.

use heapless::FnvIndexMap;

fn main() {
    const N: usize = 1 << 17;
    let mut map = FnvIndexMap::<u32, usize, N>::new();
    for i in 1..(0xffff + 3) {
        let block = i;
        let idx = i as usize - 1;
        map.insert(block, idx).unwrap();
        assert!(map.contains_key(&block), "{}", i);
    }
}

I have no idea on why this happens. Does anyone have an idea ?
EDIT: the issue is not the values but the number of keys to insert shifting the start and end of the loop leads to the same bug
EDIT 2: the bug is present in the 0.8.0 version but fixed in 0.9.0 and on the latest commit on master.
EDIT 3: the bug is not fixed in any versions

Start with the minimal reproducer using FnvIndexMap::insert and contains_key, then trace the IndexMap implementation around insertion and lookup for capacities above u16::MAX. Done means the reproducer can insert and find all keys beyond that boundary without failure.