message: Add null checks because we can
diff: @@ -137,17 +137,17 @@ fn get_context_data_mut<'a, 'b, S: Storage, Q: Querier>(
  ctx: &'a mut Ctx,
  ) -> &'b mut ContextData<'b, S, Q> {
  unsafe {
  - let data_ptr = ctx.data as *mut ContextData<S, Q>;
  - // Null-unchecked pointer to reference (https://doc.rust-lang.org/std/primitive.pointer.html#null-unchecked-version)
  - &mut *data_ptr
  + let ptr = ctx.data as *mut ContextData<S, Q>;
  + ptr.as_mut()
  + .expect("The pointer ctx.data was null in get_context_data_mut; this is a bug.")
  }
  }
  fn get_context_data<'a, 'b, S: Storage, Q: Querier>(ctx: &'a Ctx) -> &'b ContextData<'b, S, Q> {
  unsafe {
  - let data_ptr = ctx.data as *mut ContextData<S, Q>;
  - // Null-unchecked pointer to reference (https://doc.rust-lang.org/std/primitive.pointer.html#null-unchecked-version)
  - &*data_ptr
  + let ptr = ctx.data as *mut ContextData<S, Q>;
  + ptr.as_ref()
  + .expect("The pointer ctx.data was null in get_context_data; this is a bug.")
  }
  }
  