invalid encording internal server error message

[syphax-bouazzouni]

When accessing a URL containing the %aa sequence for example, such as:
https://data.stageportal.lirmm.fr/ontologies/AGROVOC/classes/%aa
the server crashes. It is related to an improper handling of URL encoding in the backend. This is the real issue, should I investigate it further? So this PR becomes irrelevant
In prod

In dev

Ref: #879