GHSA-66P5-J55P-32R9 smallvec creates uninitialized value of any type

Affected versions of this crate called mem::uninitialized to create values of a user-supplied type T. This is unsound e.g. if T is a reference type which must be non-null and thus may not remain uninitialized. The flaw was corrected by avoiding the use of mem::uninitialized, using MaybeUninit...