MT#64131 fix non-default NULL preference render

* non-default NULL value is now correctly selected
  in the UI preferences list as well as in the edit form.

Change-Id: Ief3b2e6778441c736589cfccc5a5fb7e60a7dcf0
(cherry picked from commit f6246ba094)
(cherry picked from commit 4782f68839)

lib/NGCP/Panel/Utils/Preferences.pm

@@ -1610,11 +1610,9 @@ sub create_preference_form {
             }
         }
     } elsif ($c->stash->{preference_meta}->data_type eq 'enum') {
+        $preselected_value = undef;
         if ($c->stash->{preference}->first) {
             $preselected_value = $c->stash->{preference}->first->value unless ($c->stash->{preference_meta}->data_type eq 'blob');
-        } else {
-            my $default_val = first { $_->default_val; } @{ $enums };
-            $preselected_value = $default_val ? $default_val->value : undef;
         }
     } elsif ($c->stash->{preference_meta}->max_occur == 1) {
         if ($c->stash->{preference}->first) {

share/templates/helpers/pref_table.tt

@@ -175,7 +175,7 @@
                     [% ELSIF r.data_type == "enum" %]
                         <select autocomplete="off" disabled="disabled">
                         [% FOREACH e IN r.enums %]
-                            <option [% IF r.value == e.value || (!r.value.defined && e.default_val == 1) || (!r.value.defined && !e.value.defined) %]selected="selected"[% END %]>[% e.label | html %]</option>
+                            <option [% IF r.value == e.value || (!r.value.defined && e.default_val == 1 && !e.value.defined) || (!r.value.defined && !e.value.defined) %]selected="selected"[% END %]>[% e.label | html %]</option>
                         [% END %]
                         </select>
                     [% END %]