Fix pagination parameters for Jira issue list

When no parameter was used the default was 0 after casting. This is
incorrect and the default parameters should be used.

app/services/jira/requests/issues/list_service.rb

@@ -12,8 +12,8 @@ module Jira
           super(jira_service, params)
 
           @jql = params[:jql].to_s
-          @page = params[:page].to_i || 1
-          @per_page = params[:per_page].to_i || PER_PAGE
+          @page = (params[:page] || 1).to_i
+          @per_page = (params[:per_page] || PER_PAGE).to_i
         end
 
         private

spec/services/jira/requests/issues/list_service_spec.rb

@@ -93,6 +93,16 @@ RSpec.describe Jira::Requests::Issues::ListService do
             subject
           end
         end
+
+        context 'without pagination parameters' do
+          let(:params) { {} }
+
+          it 'uses the default options' do
+            expect(client).to receive(:get).with(include('startAt=0&maxResults=100'))
+
+            subject
+          end
+        end
       end
     end
   end