Single lookup with results from different dynamic sources fails

[ddeboer]

When looking up terms in sources that share a URI (#615), and the resulting terms come from different dynamic sources (i.e. determined by the SPARQL query rather than the prefix), the query fails:

query {
  lookup(
    uris: ["https://data.muziekschatten.nl/som/d78892","https://data.muziekschatten.nl/som/ed61aa47b70e4b1d9d0ac298d823efe1"],
  ) {
    uri
    source {
      ... on Source {
        uri
        name
        creators {
          uri
          name
          alternateName
        }
      }
      ... on Error {
        __typename
        message
      }
    }        
    result {
      ... on Term {
        uri
        prefLabel
        altLabel
        hiddenLabel
        scopeNote
        seeAlso
        broader {
          uri
          prefLabel
        }
      }
      ... on Error {
        __typename
        message
      }
    }
  }
}

returns:

Cannot read properties of undefined (reading 'terms')