MultiSelect configured for server filtering sends duplicated read request on blur and open

[aleksandarevangelatov]

Bug report

MultiSelect configured for server-filtering="true" sends an empty request on focusout

     <kendo-multiselect for="SelectedOrderIds" style="width:100%"
                       placeholder="Select addresses..."
                       datatextfield="ShipName"
                       datavaluefield="OrderID"
                       filter="FilterType.Contains"
                       value="Model.SelectedOrders.Select(x=>x.OrderID)">
        <datasource type="DataSourceTagHelperType.Ajax" server-filtering="true">
            <transport>
                <read url="@Url.Page("Index", "Read")" data="forgeryToken" />
            </transport>
            <schema data="Data">
                <model id="OrderID">
                    <fields>
                        <field name="ShipName" type="string"></field>
                    </fields>
                </model>              
            </schema>
        </datasource>
    </kendo-multiselect>

Reproduction of the problem

TelerikAspNetCoreApp197.zip

1. Run the attached application
2. Enter 34, for example, and select the returned item
3. Click outside of the MultiSelect - an expected Read request is triggered.
4. Focus in the input to open the dropdown --> a non-expected Read request is triggered.

Current behavior

An empty request is sent, fetching all data.

Expected/desired behavior

A request should not be sent.

Environment

• Kendo UI version: 2021.1.330
• Browser: [all]

[gyankov]

Same behavior replicates in the jquery server filtering demo. It is not related with the server wrappers.

[aleksandarevangelatov]

Also reported in ticket 1554693

[Iankodj]

Reported in 1534530

[martintabakov]

Also reported in 1588564. Steps to reproduce on online demos in #7150