Plus sign in calendar uri / name

[t-master-t]

Steps to reproduce

1. create calendar with name "a+b"
2. try to add entries to calendar
3. for existing calendars the console displays : /remote.php/dav/calendars/user/a%2bb/ 404

Expected behaviour

Calendar entries should be displayed and no 404 should be returned in console

Actual behaviour

404 / no entries for this calendar

Server configuration

ownCloud version: (see your admin page) 10.7.0

Calendar version: (see the apps page) 1.6.4

Updated from an older installed version or fresh install:
updated from older version with existing calendar with plus character in its name. Used to work before update but it is unclear since when it stopped working

relevant db entry:
3 | principals/users/user | a+b | a+b | 1067 | a+b | 0 | #b3dc6c | NULL | VEVENT,VTODO | 0

...Suspected encoding issue