Distinguish between a null array and an empty array

[bauss via Digitalmars-d-learn]

Is there a way to do that?

Since the following are both true:
int[] a = null;
int[] b = [];

assert(a is null);
assert(!a.length);

assert(b is null);
assert(!b.length);

What I would like is to tell that b is an empty array and a is a 
null array.