Fixes the inconsistency in the #first_page method

kaminari-core/lib/kaminari/models/page_scope_methods.rb

@@ -75,7 +75,7 @@ module Kaminari
 
     # First page of the collection?
     def first_page?
-      current_page == 1
+      !out_of_range? && (current_page == 1)
     end
 
     # Last page of the collection?

kaminari-core/test/models/active_record/scopes_test.rb

@@ -340,6 +340,12 @@ if defined? ActiveRecord
           test 'not on first page' do
             assert_false model_class.page(5).per(10).first_page?
           end
+
+          test 'on first page with no record' do
+            model_class.delete_all
+
+            assert_false model_class.page(1).first_page?
+          end
         end
 
         sub_test_case '#last_page?' do