Extend CreateEffectWarhead's GetDirectHit to scan a WDist radius for hits

Instead of only the impact cell.

OpenRA.Mods.Common/Warheads/CreateEffectWarhead.cs

@@ -30,6 +30,9 @@ namespace OpenRA.Mods.Common.Warheads
 		[Desc("Remap explosion effect to player color, if art supports it.")]
 		public readonly bool UsePlayerPalette = false;
 
+		[Desc("Search radius around impact for 'direct hit' check.")]
+		public readonly WDist TargetSearchRadius = new WDist(2048);
+
 		[Desc("List of sounds that can be played on impact.")]
 		public readonly string[] ImpactSounds = new string[0];
 
@@ -72,7 +75,7 @@ namespace OpenRA.Mods.Common.Warheads
 
 		public bool GetDirectHit(World world, CPos cell, WPos pos, Actor firedBy, bool checkTargetType = false)
 		{
-			foreach (var unit in world.ActorMap.GetActorsAt(cell))
+			foreach (var unit in world.FindActorsInCircle(pos, TargetSearchRadius))
 			{
 				if (checkTargetType && !IsValidAgainst(unit, firedBy))
 					continue;