Picker should continue to be shown when a month was changed (appendDtpicker mode)

[Masanori Ohgita]

The problem occurred in "Append to Input-field" section of an example of master branch.

Reproduces:

1. Click an input field in "Append to Input-field" section. Then a picker will shown.
2. Change a month to next or previous by clicking < or > button of the picker.
3. The picker will hidden. It is problem.