Sorry, I missed that #4.
In setup described in #3, I don't even have schooltool.ldap installed.
So the error came with plain SchoolTool.
I installed my virtual machine from scratch (Ubuntu, Zentyal & SchoolTool) without Zentyal UserCorner.
Everything works now, but now I have new problem: without UserCorner I don't have any way to allow users to change their passwords (in Zentyal LDAP). :(
Sorry, I missed that #4.
In setup described in #3, I don't even have schooltool.ldap installed.
So the error came with plain SchoolTool.
I installed my virtual machine from scratch (Ubuntu, Zentyal & SchoolTool) without Zentyal UserCorner.
Everything works now, but now I have new problem: without UserCorner I don't have any way to allow users to change their passwords (in Zentyal LDAP). :(