Mutli Media Picker custom required validation not working

Questions
1

I’ve installed umbraco v 8.9 and during saving multi media picker property its custom required msg not appearing , i know that can be solved as server side validation but it exists so why not use it

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This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/104240-mutli-media-picker-custom-required-validation-not-working