When an input argument of a function evaluates to NONE
If any input argument of a function evaluates to "none", the function might not evaluate to "none". For example, ABS (NONE)=NONE, but COUNT (NONE)=0.
If any input argument of a function evaluates to "none", the function might not evaluate to "none". For example, ABS (NONE)=NONE, but COUNT (NONE)=0.