Datepicker crashes with non-standard time intervals - still an issue

[saltire]

Describe the bug
Same as #2169 - although a fix has been merged, it's still possible to get this error in v3.1.3.

To Reproduce
Steps to reproduce the behavior:

1. Go to www.reactdatepicker.com, then the "Exclude times" example
2. In the code, add the option timeIntervals={90}
3. Manually change the date in the input to July 13, 2020 2:59 PM.
4. Click the input to bring up the calendar.
5. See error: TypeError: t is undefined (Firefox), TypeError: Cannot read property 'offsetTop' of undefined (Chrome), or TypeError: undefined is not an object (evaluating 't.offsetTop') (Safari).

Expected behavior
The calendar should appear, allowing the user to select a time at a 90-minute interval, regardless of the currently selected time.

Desktop (please complete the following information):

• OS: macOS
• Browser: tested in Firefox 78, Chrome 83, and Safari 13.1.1

Additional context
It happens at many different combinations of timeIntervals and selected. Here's a test for timepicker_test.js that triggers the error in v3.1.3:

  it("should handle 90 min time intervals", () => {
    renderDatePicker("July 13, 2020 2:59 PM", {
      timeIntervals: 90,
      showTimeSelect: true
    });
    expect(getInputString()).to.equal("July 13, 2020 2:59 PM");

    ReactDOM.findDOMNode(datePicker.input).focus();

    setManually("July 13, 2020 3:00 PM");
    expect(getInputString()).to.equal("July 13, 2020 3:00 PM");
  });

[martijnrusschen]

#2350

[saltire]

Hey, thanks for merging my PR. Any idea when we'll see a release?