ices/87771.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#87771

fn main() {
    let mut arr = vec![vec![]];
    arr[0][0] = arr[0][0] = true;
}

=== stdout ===
=== stderr ===
error[E0308]: mismatched types
 --> /home/runner/work/glacier/glacier/ices/87771.rs:3:17
  |
3 |     arr[0][0] = arr[0][0] = true;
  |                 ^^^^^^^^^^^^^^^^ expected `bool`, found `()`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.
==============