Why is &array[0] @safer than array.ptr?

[Adam D. Ruppe via Digitalmars-d-learn]

On Wednesday, 25 January 2017 at 22:46:10 UTC, David Nadlinger 
wrote:
> This is because every pointer in SafeD is dereferencable.

But null pointers are allowed in SafeD and arr.ptr is either 
arr[0] or null....