Fails on latest dokuwiki rc-2020-06-09 "Hogfather" RC3

[mspacek]

It seems that /inc/JSON.php no longer exists in this version of dokuwiki, which raises this error:

[Wed Jun 10 14:41:58 2020] [:error] [pid 3091] [client 1.2.3.4] PHP Fatal error:

require_once(): Failed opening required '/var/www/dokuwiki/lib/exe/../../inc/JSON.php' 

(include_path='.:/usr/share/php:/usr/share/pear')
in /var/www/dokuwiki/lib/plugins/indexmenu/action.php
on line 160, referer: https://wikiname/somepage

This is a problem for multiple plugins.

See https://github.com/splitbrain/dokuwiki/issues/3159

[Klap-in]

Thanks for reporting. However it looks like a duplicate of #220