add sounds for grenades; fix crash in -2

OpenRA.Game/WorldUtils.cs

@@ -146,7 +146,7 @@ namespace OpenRA
 
 		public static bool IsVisible(this Actor a)
 		{
-			if (a.World.LocalPlayer.Shroud.Disabled)
+			if (a.World.LocalPlayer != null && a.World.LocalPlayer.Shroud.Disabled)
 				return true;
 
 			var shroud = a.World.WorldActor.traits.Get<Shroud>();

mods/ra/weapons.yaml

@@ -191,6 +191,7 @@ Hellfire:
 Grenade:
 	ROF: 60
 	Range: 4
+	Report: grenade1
 	Bullet:
 		Speed: 5
 		High: true
@@ -206,6 +207,7 @@ Grenade:
 		InfDeath: 2
 		SmudgeType: Crater
 		Damage: 50
+		ImpactSound: kaboom12
 
 75mm:
 	ROF: 40