Added zero check to make undo mipmap bias offset an idempotent operation

Assets/Scripts/Core/Fsr2Callbacks.cs

@@ -97,6 +97,9 @@ namespace FidelityFX
 
         public virtual void UndoMipmapBias()
         {
+            if (CurrentBiasOffset == 0f)
+                return;
+
             ApplyMipmapBias(-CurrentBiasOffset);
         }
     }