Added Required attribute to Text property of MessageCommand.

Jellyfin.Api/Controllers/SessionController.cs

@@ -323,13 +323,6 @@ namespace Jellyfin.Api.Controllers
             [FromRoute, Required] string sessionId,
             [FromBody, Required] MessageCommand command)
         {
-
-            // Need to check if message.Text is null, since [Required] can't be applied to properties of a deserialized object.
-            if (string.IsNullOrWhiteSpace(command.Text))
-            {
-                throw new ArgumentNullException("Message Text may not be empty.");
-            }
-
             var nullCorrectedCommand = new MessageCommand
             {
                 Header = string.IsNullOrWhiteSpace(command.Header) ? "Message from Server" : command.Header,

MediaBrowser.Model/Session/MessageCommand.cs

@@ -1,12 +1,14 @@
 #nullable disable
 #pragma warning disable CS1591
 
+using System.ComponentModel.DataAnnotations;
+
 namespace MediaBrowser.Model.Session
 {
     public class MessageCommand
     {
         public string Header { get; set; }
-
+        [Required(AllowEmptyStrings = false)]
         public string Text { get; set; }
 
         public long? TimeoutMs { get; set; }