weight correctness throws 500

[cbizon]

With aragorn as a wf engine, I can call score w/o running omnicorp and it creates a 500. I would expect it to do something more sensible.

This errors:

{
    "message": {
        "query_graph": {
            "nodes": {
                "n0": {
                    "ids": [
                        "NCBIGene:6611"
                    ],
                    "categories": [
                        "biolink:Gene"
                    ]
                },
                "n1": {
                    "categories": [
                        "biolink:ChemicalSubstance"
                    ]
                }
            },
            "edges": {
                "e01": {
                    "subject": "n0",
                    "object": "n1"
                }
            }
        }
    },
    "log_level": "DEBUG",
    "workflow": [
        "lookup",
        "score"
    ]
}

But replacing workflow with:

"workflow": [
        "lookup",
        "connect_knodes",
        "score"
    ]

succeeds.