Server error when querying UNII:2ZM8CX04RZ with drug_chemical_conflate turned on

[gaurav]

This currently produces a 500 server error: https://nodenorm-es.ci.transltr.io/get_normalized_nodes?curie=UNII:2ZM8CX04RZ&conflate=true&drug_chemical_conflate=true

The query works fine with drug_chemical_conflate=false:
https://nodenorm-es.ci.transltr.io/get_normalized_nodes?curie=UNII:2ZM8CX04RZ&conflate=true&drug_chemical_conflate=true

This is what the result should look like: https://nodenorm.ci.transltr.io/get_normalized_nodes?curie=UNII:2ZM8CX04RZ&conflate=true&drug_chemical_conflate=true