Minor fix in resource
Minor fix in resource

When a request fails, we don't want to add another error by calling
match on a non existant header

Masoumeh/arethusa,PonteIneptique/arethusa,PonteIneptique/arethusa,fbaumgardt/arethusa,fbaumgardt/arethusa,alpheios-project/arethusa,latin-language-toolkit/arethusa,fbaumgardt/arethusa,alpheios-project/arethusa,Masoumeh/arethusa,alpheios-project/arethusa,latin-language-toolkit/arethusa