Add property requirements to safe traits

OpenRA.Mods.Common/Traits/Crates/ExplodeCrateAction.cs

@@ -17,7 +17,7 @@ namespace OpenRA.Mods.Common.Traits
 	class ExplodeCrateActionInfo : CrateActionInfo
 	{
 		[Desc("The weapon to fire upon collection.")]
-		[WeaponReference] public string Weapon = null;
+		[WeaponReference, FieldLoader.Require] public string Weapon = null;
 
 		public override object Create(ActorInitializer init) { return new ExplodeCrateAction(init.Self, this); }
 	}

OpenRA.Mods.Common/Traits/Crates/GiveUnitCrateAction.cs

@@ -19,7 +19,7 @@ namespace OpenRA.Mods.Common.Traits
 	class GiveUnitCrateActionInfo : CrateActionInfo
 	{
 		[Desc("The list of units to spawn.")]
-		[ActorReference]
+		[ActorReference, FieldLoader.Require]
 		public readonly string[] Units = { };
 
 		[Desc("Races that are allowed to trigger this action")]

OpenRA.Mods.Common/Traits/Crates/GrantUpgradeCrateAction.cs

@@ -16,7 +16,7 @@ namespace OpenRA.Mods.Common.Traits
 	[Desc("Grants an upgrade to the collector.")]
 	public class GrantUpgradeCrateActionInfo : CrateActionInfo
 	{
-		[UpgradeGrantedReference]
+		[UpgradeGrantedReference, FieldLoader.Require]
 		[Desc("The upgrades to apply.")]
 		public readonly string[] Upgrades = { };
 

OpenRA.Mods.Common/Traits/Crates/SupportPowerCrateAction.cs

@@ -17,7 +17,7 @@ namespace OpenRA.Mods.Common.Traits
 	class SupportPowerCrateActionInfo : CrateActionInfo
 	{
 		[Desc("Which proxy actor, which grants the support power, to spawn.")]
-		[ActorReference] public readonly string Proxy = null;
+		[ActorReference, FieldLoader.Require] public readonly string Proxy = null;
 
 		public override object Create(ActorInitializer init) { return new SupportPowerCrateAction(init.Self, this); }
 	}