argument 0 (zero) vs. integer 0

I have an integer CCK field called 'friends'. If I want a view showing all nodes with 'friends' value = 0 (zero) an pass 0 as an argument that won't work. (0 seems to mean "no value" or NULL to views instead, but not 0 as an integer). So how can I display all nodes with 0 'friends' then? I found a workaround on coincidence by using not 0 but a letter like 'a' as argument to display all nodes with values 0, but that does not seem to be a proofen way for all future updates I guess.

Isn't it a bug, that an argument '0' is not matching 0-integers?

(BTW: Why are there no real boolean variable types in CCK?)