Major Description
A user reported on the mailing list:
The following RUTA grammar:
DECLARE Annotation A;
DECLARE Annotation B;
DECLARE Annotation C(Annotation a, Annotation b);
W{REGEXP("A")->MARK(A)};
W{REGEXP("B")->MARK(B)};
A B?{-> GATHER(C, 1, 2, "a" = 1, "b" = 2)};
Run s as expected on the input "A B C", but gets a NullPointerException on
"A X C", presumably because the 2 index is not mapped to anything.