Fix SoundscapeTrigger error if source or SoundFile is not valid

Author: trende2001

engine/Sandbox.Engine/Scene/Components/Audio/SoundscapeTrigger.cs

@@ -317,6 +317,12 @@ public LoopedSoundEntry( Soundscape.LoopedSound sound, float internalVolume, flo
 
 		public override void Frame( in Transform head )
 		{
+			if ( source == null || !source.SoundFile.IsValid() )
+			{
+				Finished = true;
+				return;
+			}
+
 			var targetVolume = sourceVolume * internalVolume * Volume;
 			if ( Finished ) targetVolume = 0.0f;
 
@@ -374,6 +380,12 @@ public override void Frame( in Transform head )
 			if ( timeUntilNextShot > 0 )
 				return;
 
+			if ( source == null || !source.SoundFile.IsValid() )
+			{
+				Finished = true;
+				return;
+			}
+
 			timeUntilNextShot = source.RepeatTime.GetValue();
 
 			handle?.Stop( 0.1f );