Transform for `RDL` fails about bioportal-to-kgx HOT 4 CLOSED

Also ESSO, with a very similar error.

I think this occurs if "data.bioontology.org" isn't present in the header of the input file for whatever reason, though this is the first line of the input for ESSO:

## GRAPH http://data.bioontology.org/ontologies/ESSO/submissions/5

from bioportal-to-kgx.

And this is the first line of RDL:

## GRAPH http://data.bioontology.org/ontologies/RDL/submissions/1

from bioportal-to-kgx.

For comparison, here is the header for DRON:

## GRAPH http://data.bioontology.org/ontologies/DRON/submissions/14

No obvious difference here.

from bioportal-to-kgx.

Similar to #58 , so these should complete on retry.
Should still try to catch the IndexError so it doesn't stop transform runs prematurely.

from bioportal-to-kgx.