Remove uses of IsValid because null checks work

These were used because null checks on UnityEngine.Objects were broken, but this bug has been fixed for a year+ and these calls cause ambiguity and failed compiles in any projects with ShaderGraph imported because Unity made the very poor choice to name a top level namespace 'Utilities'

Author: MerlinVR

Assets/USharpVideo/Scripts/USharpVideoPlayer.cs

@@ -1476,9 +1476,9 @@ public void UnregisterScreenHandler(VideoScreenHandler screenHandler)
             }
         }
 
-        Texture _lastAssignedRenderTexture;
+        private Texture _lastAssignedRenderTexture;
 
-        void UpdateRenderTexture()
+        private void UpdateRenderTexture()
         {
             if (_registeredScreenHandlers == null)
                 return;
@@ -1490,8 +1490,10 @@ void UpdateRenderTexture()
 
             foreach (VideoScreenHandler handler in _registeredScreenHandlers)
             {
-                if (Utilities.IsValid(handler))
+                if (handler)
+                {
                     handler.UpdateVideoTexture(renderTexture, IsUsingAVProPlayer());
+                }
             }
 
             _lastAssignedRenderTexture = renderTexture;
@@ -1509,7 +1511,7 @@ void UpdateRenderTexture()
         [PublicAPI]
         public void RegisterCallbackReceiver(UdonSharpBehaviour callbackReceiver)
         {
-            if (!Utilities.IsValid(callbackReceiver))
+            if (!callbackReceiver)
                 return;
 
             if (_registeredCallbackReceivers == null)
@@ -1531,7 +1533,7 @@ public void RegisterCallbackReceiver(UdonSharpBehaviour callbackReceiver)
         [PublicAPI]
         public void UnregisterCallbackReceiver(UdonSharpBehaviour callbackReceiver)
         {
-            if (!Utilities.IsValid(callbackReceiver))
+            if (!callbackReceiver)
                 return;
 
             if (_registeredCallbackReceivers == null)
@@ -1559,11 +1561,11 @@ public void UnregisterCallbackReceiver(UdonSharpBehaviour callbackReceiver)
             }
         }
 
-        void SendCallback(string callbackName)
+        private void SendCallback(string callbackName)
         {
             foreach (UdonSharpBehaviour callbackReceiver in _registeredCallbackReceivers)
             {
-                if (Utilities.IsValid(callbackReceiver))
+                if (callbackReceiver)
                 {
                     callbackReceiver.SendCustomEvent(callbackName);
                 }

Assets/USharpVideo/Scripts/VideoControlHandler.cs

@@ -5,7 +5,6 @@
 using UnityEngine.UI;
 using VRC.SDK3.Components;
 using VRC.SDKBase;
-using VRC.Udon;
 
 namespace UdonSharp.Video
 {
@@ -130,7 +129,7 @@ void UpdateMaster()
             if (masterField)
             {
                 VRCPlayerApi owner = Networking.GetOwner(gameObject);
-                if (Utilities.IsValid(owner))
+                if (owner != null && owner.IsValid())
                     masterField.text = Networking.GetOwner(gameObject).displayName;
             }
 #endif