PyReason bug for certain type of rules

[jaikrishnap98]

The following rule where variable of one of the unary predicate in body clause is not used in any binary predicate in the body but directly used in the head of the rule, groundings are done incorrectly in current implementation of PyReason:

isConnectedTo(A, Y) <-1 isConnectedTo(Y, B), Vnukovo_International_Airport(A), Amsterdam_Airport_Schiphol(B)