pam: Could not set 'present' on ensure: undefined method `each' for nil:NilClass if arguments is not define

The following code breaks puppet:
```
    pam { 'include_password-auth':
      service  => 'sshd',
      type     => 'auth',
      module   => 'password-auth',
      control  => 'include',
      position => 'after last',
    }
```

Here is the error:
```
Error: Could not set 'present' on ensure: undefined method `each' for nil:NilClass at 98:/***.pp
/var/lib/puppet/lib/puppet/provider/pam/augeas.rb:106
/var/lib/puppet/lib/augeasproviders/provider.rb:701:in `call'
/var/lib/puppet/lib/augeasproviders/provider.rb:701:in `augopen_internal'
/var/lib/puppet/lib/augeasproviders/provider.rb:146:in `augopen!'
/var/lib/puppet/lib/augeasproviders/provider.rb:786:in `augopen!'
/var/lib/puppet/lib/augeasproviders/provider.rb:201:in `create'
/usr/lib/ruby/site_ruby/1.8/puppet/property/ensure.rb:16:in `set_present'
/usr/lib/ruby/site_ruby/1.8/puppet/property.rb:197:in `send'
/usr/lib/ruby/site_ruby/1.8/puppet/property.rb:197:in `call_valuemethod'
/usr/lib/ruby/site_ruby/1.8/puppet/property.rb:498:in `set'
.....
```

Adding a ''arguments => []'' works:
```
    pam { 'include_password-auth':
      service  => 'sshd',
      type     => 'auth',
      module   => 'password-auth',
      control  => 'include',
      position => 'after last',
      arguments => []
    }
```