Fix an issue with loops

[sonmarcho]

The following example caused a crash:

pub struct BigInt<const N: usize>(pub [u64; N]);

impl<const N : usize> BigInt<N> {
  pub fn const_geq(&self, other: &Self) -> bool {
      let mut i = 0;
      while i < N {
          let a = self.0[i];
          i += 1;
      }
      false
  }
}

The reason is that when reorganizing the environment upon reaching the continue statement, we did not move some value to an anonymous value, while in the fixed-point environment this value was bottom. The matcher then failed upon matching those two environments.