Seen in both 0.91 dev and 0.91 stable:
Steps to reproduce, in Firefox:
- Put two dtpickers on the page, instantiated however you like.
- Make the following call:
```
$("#first-time-picker").datetimepicker('option', 'minDate', null);
```
- If the second datetimepicker had a value equal to the empty string, then it will now receive the current datetime as its value, even though the call from step 2 (seemingly) makes no call to the second time picker. It should remain blank, as it does with the plain, old datepicker.