Issue with NgbDateAdapter when used with a Datepicker on an input

[msosa]

Bug description:

Using NgbDateAdapter with anything other than the original NgbDateStruct will not work with a datepicker on an input. It looks like this was missed in my previous PR and when selecting a date from the popup it will show as blank on the input even though the model gets updated. I have something sort of working but having issues with dealing with any type of invalid input and it just causes it to crash. If i take out the second ternary here in datepicker-input on the function manualDateChange, it does end up fixing the crashing error after all my other changes. Not sure if that is the right solution though.

 this._onChange(this._model ? this._model.toStruct() : (value === '' ? null : value));

If it helps I can open up a PR with the potential fix

Link to minimally-working plunker that reproduces the issue:

As this is not yet released I cannot make a plunker

Version of Angular, ng-bootstrap, and Bootstrap:

ng-bootstrap: master branch

[maxokorokov]

Indeed, we kinda forgot about the ngbInputDatepicker...