bad urlencoding results in 500 error from server

[ilawjr]

Description:
Sending a curl request with an incorrectly encoded parameter results in a 500 error.
This is with themis-v0.4.3-1

curl "https://[themis-server]:8080/issue?pid=%hello" --key ./base.key --cert ./CommonNamed.crt -i
HTTP/1.1 500 Internal Server Error
Content-Type: text/plain; charset=utf-8
X-Midt-Server: issuer
X-Midt-Version: 0.4.3
Date: Tue, 31 Mar 2020 19:32:52 GMT
Content-Length: 24
Connection: close

Expected:
a 400 error.