Improve GeoNode#project_ids to save one query

app/models/geo_node.rb

@@ -109,9 +109,9 @@ class GeoNode < ActiveRecord::Base
   end
 
   def project_ids
-    return unless namespaces.any?
-
-    namespaces.flat_map { |namespace| namespace.all_projects.pluck(:id) }.uniq
+    namespaces.flat_map { |namespace| namespace.all_projects.select(:id).pluck(:id) }
+              .uniq
+              .presence
   end
 
   private

spec/models/geo_node_spec.rb

@@ -318,14 +318,14 @@ describe GeoNode, type: :model do
   end
 
   describe '#project_ids' do
-    context 'without group restriction' do
+    context 'without namespace restriction' do
       it 'returns nil' do
         expect(node.project_ids).to be_nil
       end
     end
 
-    context 'with group restrictions' do
-      it 'returns an array with unique project ids that belong to the groups' do
+    context 'with namespace restrictions' do
+      it 'returns an array with unique project ids that belong to the namespaces' do
         group_1 = create(:group)
         group_2 = create(:group)
         nested_group_1 = create(:group, parent: group_1)