[Templates] array.size returns undef instead of zero when array is empty

[Myk Melez]

Calling the "size" virtual function on an empty array returns the 
undefined value.  This is consistent with Perl behavior 
(scalar(@empty_array) returns undefined) but inconsistent with what I 
would expect when calling the "size" virtual function in TT.  Shouldn't 
the function return numeric zero in this situation?

-myk