Steps to reproduce:

1. Use unsplash as DAM connector.
2. Add imageasset fieldtype to Article Content Type with asset identifier.
3. Create new Article and pick image asset from DAM.
4. Run php bin/console ibexa:graphql:generate-schema command.
5. Access /graphiql URL.
6. Run the following request:

   {
       content {
         articles {
           edges {
             node {
               title
               asset {
                 uri
               }
             }
           }
         }
       }
   }
   

Result:
You will be presented with an exception:

Could not find 'Content' with identifier 'findSingle() found no content for the given $criterion

Expected result:
The query result should be presented without an exception.

Note:
Problem doesn't occur with standard imageasset fieldtype.