Hours drop down loaded with blank on configuring hours step interval as 3

Hours drop down loaded with blank on configuring hours step interval as 3

Here is the code:

function setMinMaxTime(min, max){
$('#rest_example_1').datetimepicker({
controlType:'select',
stepHour:3,
hourMin: 1,
hourMax: 20,
timeFormat: 'hh:mm tt'
}).datetimepicker();
}

<input type="text" name="rest_example_1" id="rest_example_1" value="" onclick="setMinMaxTime(8,16);"/>

if "stepHour:1" then selected hour is populating in hours drop down list and if we change it to "stepHour:3" then selected hour is not selected and showing blank in hours drop down list.