Set null as function array parameter

[Oleg via Digitalmars-d-learn]

Hello. How can I call a function with null as parameter, which I 
don't want to set. For example:
void foo(ref int[] param1) {}
I can't call this function like:
foo(null);
Is it possible to set default value for an array parameter or 
pass null/empty array? I can create empty array and pass it, but 
it looks ugly:
int[] x;
foo(x);

Thanks.