Pagination: fix a potential exception with new deps

packages/pagination/src/pagination.js

@@ -74,6 +74,8 @@ export default {
     const rightWrapper = <div class="el-pagination__rightwrapper"></div>;
     let haveRightWrapper = false;
 
+    template.children = template.children || [];
+    rightWrapper.children = rightWrapper.children || [];
     components.forEach(compo => {
       if (compo === '->') {
         haveRightWrapper = true;