Explicit header definition required for curl converter queries

curl converter queries composed as indicated in the documentation fail.

curl 'https://minerva-service.uni.lu/minerva/api/convert/GPML:SBML' -i -X POST --data-binary @file.gpml returns

HTTP/1.1 500 {"reason":"Problem with input data","error":"Internal server error."}

The problem is fixed by adding an explicit header information. Surprisingly, the query passed with

-H 'Content-Type: application/json' and worked as expected for application/xml