Gracefully handle nil collections when paging

lib/google/apis/core/base_service.rb

@@ -63,11 +63,12 @@ module Google
           item_count = 0
           loop do
             @last_result = @fetch_proc.call(page_token)
-            for item in @last_result.send(@items_field)
+            items = @last_result.send(@items_field)
+            for item in items
               item_count = item_count + 1
               break if @max && item_count > @max
               yield item
-            end
+            end unless items.nil?
             break if @max && item_count >= @max
             break if @last_result.next_page_token.nil? || @last_result.next_page_token == page_token
             page_token = @last_result.next_page_token

spec/google/apis/core/service_spec.rb

@@ -265,6 +265,11 @@ EOF
         expect(items).to contain_exactly('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i')
       end
 
+      it 'should ignore nil collections' do
+        responses['p1'].items = nil
+        expect(items).to contain_exactly('a', 'b', 'c', 'g', 'h', 'i')
+      end
+
       it 'should allow selecting another field for items' do
         expect(service.fetch_all(items: :alt_items) { |token| responses[token] } ).to contain_exactly(1, 2, 3, 4, 5, 6, 7, 8, 9)
       end
@@ -307,7 +312,6 @@ EOF
 
         expect(count).to eq 6
       end
-
     end
   end
 end