DateRangePicker: unable to select when initial_visible_month is not given

[emmanuelle]

With

from datetime import datetime as dt

dcc.DatePickerRange(
    id='date-picker-range',
    start_date = dt(2017, 1, 31),
    end_date = dt(2018, 3, 21),
    min_date_allowed = dt(2017, 1, 31),
    max_date_allowed = dt(2018, 3, 21),
)

the component is not responsive (nothing can be selected), whereas with

from datetime import datetime as dt

dcc.DatePickerRange(
    id='date-picker-range',
    start_date = dt(2017, 1, 31),
    end_date = dt(2018, 3, 21),
    min_date_allowed = dt(2017, 1, 31),
    max_date_allowed = dt(2018, 3, 21),
    initial_visible_month=dt(2017, 1, 31)
)

it's OK. If the start_date is given but not initial_visible_month, then initial_visible_month could default to start_date.