datepicker close when changing month

It looks likes this bug occurs again :
https://github.com/amsul/pickadate.js/issues/112

Clicking the 'next month' button _without any value in the input_ close the the datepicker

Tested with FF 40.0.2 & Chrome 44.0.2403.157 m & Safari 5.1.7 (all on PC with win 8.1)

Anyone got an idea of what the source of this issue is ?

And BTW thank you for sharing this awesome work, it's a pleasure to work with !

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edit :
- i found an ugly workaround : put my placeholder text as inital value of the date field
- in this case, to prevent the placeholder value to being sended, you'll need to run `onStart: function () { this._hidden.value=''; }` when you have no value set to the form field