[RMLTC0019b-JSON] Expected output should be the same as RMLTC0019a-JSON

[s-minoo]

Problem

Currently, the test case's expected output is an empty dataset even though the mapping document is
the same as the one used in RMLTC0019a-JSON.

The only difference is the addition of the following JSON record in the input data file:

{
      "ID": 30,
      "FirstName": "Juan Daniel",
      "LastName": "Crespo"
}

which results in an error when generating the subject IRI since the subject map is using rml:reference for the
reference expression $.FirstName without any IRI validations.

This error doesn't happen with the other two JSON records (the same input as the test case RMLTC0019a-JSON) :

{
      "ID": 10,
      "FirstName": "http://example.com/ns#Jhon",
      "LastName": "Smith"
    
},
{
      "ID": 20,
      "FirstName": "Carlos",
      "LastName": "Mendoza"
 },

Thus, the expected output should be the same as those of RMLTC0019a-JSON:

<http://example.com/ns#Jhon> <http://xmlns.com/foaf/0.1/name> "http://example.com/ns#Jhon" .
<http://example.com/base/Carlos> <http://xmlns.com/foaf/0.1/name> "Carlos" .