Can confirm this patch fixes the issue, so
Tested-by: Friedrich Weber
Steps to reproduce:
1) Create LDAP realm with default sync settings
2) Edit LDAP realm, go to sync settings tab, enter values in all text
boxes except one (e.g. all except "Group filter")
3) Click OK
On current master, th
...when editing LDAP realm sync settings and only a single property is
empty and thus to be deleted (e.g. values.delete = "filter").
If `delete` is a simple string and not an array,
`PVE.Utils.delete_if_default` simply creates a comma-separated list,
(e.g. value.delete = "filter,sync-attributes").
