fix(converter): keep x-nullable in shared $ref responses#2276

esaezgil wants to merge 2 commits intoswagger-api:masterswagger-api/swagger-parser:masterfrom

esaezgil:bug/2269_fix_lost_xnullable_swagger_2_shared_responsesesaezgil/swagger-parser:bug/2269_fix_lost_xnullable_swagger_2_shared_responsesCopy head branch name to clipboard