cryptovec: use NonNull::dangling instead of potentially dangled member pointer

Dependencies

• [2] 7FRJYUI6 Reboot because of a bad change

Change contents

• edit in cryptovec/src/lib.rs at line 29
  [2.428990]→[2.428990:429004](∅→∅)
  − zero: u8,
• replacement in cryptovec/src/lib.rs at line 137
  [2.431586]→[2.431586:431657](∅→∅)
  − let mut buf = CryptoVec {

  − p: std::ptr::null_mut(),
  [2.431586]

  [2.431657]
  + CryptoVec {

  + p: std::ptr::NonNull::dangling().as_ptr(),
• replacement in cryptovec/src/lib.rs at line 141
  [2.431703]→[2.431703:431846](∅→∅)
  − zero: 0,

  − };

  − // This avoids potential problems in as_slice().

  − buf.p = &mut buf.zero;

  − //

  − buf
  [2.431703]

  [2.431846]
  + }
• edit in cryptovec/src/lib.rs at line 193
  [2.433177]→[2.433177:433202](∅→∅)
  − zero: 0,
• edit in cryptovec/src/lib.rs at line 208
  [2.433686]→[2.433686:433711](∅→∅)
  − zero: 0,