Some of the predicate invention examples don't work in latest version

[yangdinglou]

Here is the output of the classic kinship example. I have checked that no PI is performed during the search.

Precision:1.00 Recall:1.00 TP:19 FN:0 TN:0 FP:0 Size:13
ancestor(A,B):- father(A,B).
ancestor(A,B):- mother(A,B).
ancestor(A,B):- father(C,B),mother(A,C).
ancestor(A,B):- father(A,C),ancestor(C,B).
ancestor(A,B):- father(C,B),ancestor(A,C).

If this is not easy to fix, could you tell me which commit is the most recent one whose PI works?