Wrong type when there is more than one alias in AD field proxyAddresses

[andreashaerter]

The used library returns a string if there is only one address listed in Active Directory's proxyAddresses and an array if there are multiple. The plugin expects to parse a CSV string for the latter case, but gets an array, resulting in a type error.

This only happens if

1. $config['identity_from_directory_handle_proxyaddresses'] is set to true
2. There is more then one alias address stored in the user's proxyAddresses field.