Datepicker enable after select symbol

I have a 2 fields, symbol and date, if symbol is select after datepicker is enable, without select symbol datepicker is disable.

<div class="form-group col-sm-10">
                {!! Form::label('symbol', 'Symbals:') !!}
                {!! Form::select('symbol_id', [''=>'Choose market']  , null, ['class'=>'form-control', 'id'=>'symbol'])!!}
            </div>
<div class="form-group col-lg-5">
                {!! Form::label('tradedate', 'Traded date:') !!}
                <div class=" input-append date form_datetime" data-date="" data-date-format="dd MM yyyy - HH:ii p" data-link-field="dtp_input1">
                    <input size="16" type="text" value="" readonly class="form-control">
                    <span class="add-on"><i class="icon-remove"></i></span>
                    <span class="add-on"><i class="icon-th"></i></span>
                </div>
                <input type="hidden" id="dtp_input1" value="" name="tradedate" />
            </div>

via Chebli Mohamed