Problem:
When submitting the LDAP settings form without specifying the mandatory field "User password", the form is accepted and no error messages are returned.

Steps to reproduce:

1. Navigate to Administration => Authentication => LDAP Settings
2. Enable "Enable LDAP authentication" option
3. Fill in all mandatory fields with valid data, except for field "User password" - leave it blank
4. Press "Test" button
5. Press Save button

Result:
1 - When pressing the "Test" button no response message is returned
2 - When pressing the "Update" button an "Authentication settings updated" message is returned.

Expected:
User password field is marked as mandatory, therefore, in both cases an error message should be returned, stating thet the "User password" parameter cannot be empty.