Fix to an invalid json request detection leading to the JSON export failing
Fix to an invalid json request detection leading to the JSON export failing

- It seems like relying on the Accept header can lead to the data type detection failing when accessing .json extension views
- this issue seems to have gone unnoticed since until now the data passed to the json view was the same as that passed to the html view
- this means that all the additional UI only features may have triggered in the background previously on .json views

FloatingGhost/MISP,crruthe/MISP,devnull-/MISP,crruthe/MISP,RichieB2B/MISP,cristianbell/MISP,FIRSTdotorg/MISP,SteveClement/MISP,MISP/MISP,FloatingGhost/MISP,Rafiot/MISP,Rafiot/MISP,FIRSTdotorg/MISP,devnull-/MISP,Rafiot/MISP,FloatingGhost/MISP,MISP/MISP,Rafiot/MISP,MISP/MISP,devnull-/MISP,SteveClement/MISP,FIRSTdotorg/MISP,cristianbell/MISP,MISP/MISP,cristianbell/MISP,cristianbell/MISP,TheDr1ver/MISP,FloatingGhost/MISP,RichieB2B/MISP,RichieB2B/MISP,crruthe/MISP,SteveClement/MISP,TheDr1ver/MISP,MISP/MISP,TheDr1ver/MISP,RichieB2B/MISP,SteveClement/MISP,FIRSTdotorg/MISP,crruthe/MISP,SteveClement/MISP,TheDr1ver/MISP,devnull-/MISP