[rules-users] Simple Disjunction Question

Hi there Assume we have a rule like this: when $a : A(a==1) or ($b : B(b==1) and $c : C(c==1)) then do($a) do($b) do($c) end Assuming also, that for some reason I do not want to split this rule into two. Then, I get a NullPointer exception because either $a or $b and $c are not defined. Is there a way to catch or check for this. Thanks so much for any help Thomas