Datepicker: Fixed #5022 numberOfMonths with one column multiple rows doesn't display the next button

Author: kbwood

ui/jquery.ui.datepicker.js

@@ -1412,12 +1412,15 @@ $.extend(Datepicker.prototype, {
 				var cornerClass = ' ui-corner-all';
 				var calender = '';
 				if (isMultiMonth) {
-					calender += '<div class="ui-datepicker-group ui-datepicker-group-';
-					switch (col) {
-						case 0: calender += 'first'; cornerClass = ' ui-corner-' + (isRTL ? 'right' : 'left'); break;
-						case numMonths[1]-1: calender += 'last'; cornerClass = ' ui-corner-' + (isRTL ? 'left' : 'right'); break;
-						default: calender += 'middle'; cornerClass = ''; break;
-					}
+					calender += '<div class="ui-datepicker-group';
+					if (numMonths[1] > 1)
+						switch (col) {
+							case 0: calender += ' ui-datepicker-group-first';
+								cornerClass = ' ui-corner-' + (isRTL ? 'right' : 'left'); break;
+							case numMonths[1]-1: calender += ' ui-datepicker-group-last';
+								cornerClass = ' ui-corner-' + (isRTL ? 'left' : 'right'); break;
+							default: calender += ' ui-datepicker-group-middle'; cornerClass = ''; break;
+						}
 					calender += '">';
 				}
 				calender += '<div class="ui-datepicker-header ui-widget-header ui-helper-clearfix' + cornerClass + '">' +