MdBootstrap multi select Select All option not working

Team,

We are using MDB Pro 4.5.9 version and we are using multi select plugin

Where in if we are selecting Select option and try to read the selected values we are getting null , If I choose one of the option I am getting value

Below is the sample code.

<select id="mdselect" class="mdb-select colorful-select dropdown-primary" multiple searchable="Search..">

                <option value="" disabled selected>Select</option>

                <option value="1">A</option>

                <option value="2">B</option>

                <option value="3">C</option>

                <option value="4">D</option>

</select>

Initialization : $('.mdb-select').material_select();

When we choose select all and try to read $(“# mdselect”).val() -> “”

When we choose select option A and try to read $(“# mdselect”).val() -> “1”

Could you please help us is this an existing issue as part of this version , if yes Could you please help me if we have resolution