Add property requirements to safe traits

OpenRA.Mods.RA/Traits/Buildings/ClonesProducedUnits.cs

@@ -17,6 +17,7 @@ namespace OpenRA.Mods.RA.Traits
 	[Desc("Creates a free duplicate of produced units.")]
 	public class ClonesProducedUnitsInfo : ITraitInfo, Requires<ProductionInfo>, Requires<ExitInfo>
 	{
+		[FieldLoader.Require]
 		[Desc("Uses the \"Cloneable\" trait to determine whether or not we should clone a produced unit.")]
 		public readonly string[] CloneableTypes = { };
 

OpenRA.Mods.RA/Traits/Cloneable.cs

@@ -16,6 +16,7 @@ namespace OpenRA.Mods.RA.Traits
 	[Desc("Actors with the \"ClonesProducedUnits\" trait will produce a free duplicate of me.")]
 	public class CloneableInfo : TraitInfo<Cloneable>
 	{
+		[FieldLoader.Require]
 		[Desc("This unit's cloneable type is:")]
 		public readonly string[] Types = { };
 	}

OpenRA.Mods.RA/Traits/Infiltration/InfiltrateForSupportPower.cs

@@ -15,7 +15,7 @@ namespace OpenRA.Mods.RA.Traits
 {
 	class InfiltrateForSupportPowerInfo : ITraitInfo
 	{
-		[ActorReference] public readonly string Proxy = null;
+		[ActorReference, FieldLoader.Require] public readonly string Proxy = null;
 
 		public object Create(ActorInitializer init) { return new InfiltrateForSupportPower(this); }
 	}

OpenRA.Mods.RA/Traits/LeavesHusk.cs

@@ -18,7 +18,7 @@ namespace OpenRA.Mods.RA.Traits
 	[Desc("Spawn another actor immediately upon death.")]
 	public class LeavesHuskInfo : ITraitInfo
 	{
-		[ActorReference]
+		[ActorReference, FieldLoader.Require]
 		public readonly string HuskActor = null;
 
 		public object Create(ActorInitializer init) { return new LeavesHusk(init, this); }