The use of this extension with Mediawiki version 1.42 causes dysfunction.
I found the 2 errors which are the same 2.
You must modify in the "extrightfunctions.php" file, line 140 and 170.
Initially these lines are:
-> Getsereffectivegroups ($ user, usergroupManager :: Read_normal,! $ wgrightfunctionsallowcaching);
And it must be replaced by:
-> Getsereffectivegroups ($ User, Idbaccessobject :: Read_normal,! $ wgrightfunctionsallowcaching);
Errors have disappeared and the extension works normally again.
There may be another solution, but I don't know Mediawiki correctly.