[DF] Fix out of bounds access in AddDSColumns
[DF] Fix out of bounds access in AddDSColumns

The Aggregate method was calling CheckAndFillDSColumns with an index sequence
of length 2 rather than 1 (the aggregator lambda does take 2 arguments,
but only the second corresponds to an RDF column). This resulted in
a harmless out of bounds access in a vector<bool>: two bits were checked
rather than one, but because of bit-packing the capacity of a vector<bool>
is always a multiple of 8 so this never resulted in access to invalid
memory (and because of zero-initialization, the out-of-bounds values always
happened to read to the harmless, "correct" value, `false`).

olifre/root,karies/root,karies/root,karies/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,karies/root,karies/root,karies/root,olifre/root,olifre/root,olifre/root,olifre/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,karies/root,root-mirror/root,olifre/root,olifre/root