Fix: person details when fn and gn are missing

[rawmain]

This PR fixes output display issues with those certificates that don't include the fn (familyName) and gn (givenName) fields, but for instance only the fnt field.

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Issue Details :

Some foreign certificates only include the fnt field = no fn and gn fields. Therefore - owing to the current declaration of fun setPersonData - the validation output of such certificates doesn't contain any person details of the certificate holder.

• Reference : https://github.com/ministero-salute/it-dgc-verificac19-sdk-android/issues/119

• You can check against the DGC ACC samples inside the official EU DGCA Quality Assurance repo, for instance SG 1.3.0

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Fix description :

It checks if the fn field name is null/empty.

• If true setPersonData uses the fnt + gnt + gn fields in order to arrange the text for the person details into the validation output.
• Otherwise setPersonData uses fn + gn .

[rawmain]

@it-eucert-team + @nicola-95 + @Kaizen-7 + @astagi

Fix is working flawlessly with current develop + feature code, so there should be no issues to include it in the upcoming 1.2.5 release.

Already submitted the same fix PR for iOS too.