Ignore nonexistent actors in D2k importer code instead of crashing.

OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs

@@ -371,8 +371,9 @@ namespace OpenRA.Mods.D2k.UtilityCommands
 				{
 					var kvp = ActorDataByActorCode[tileSpecialInfo];
 					if (!rules.Actors.ContainsKey(kvp.Actor.ToLowerInvariant()))
-						throw new InvalidOperationException($"Actor with name {kvp.Actor} could not be found in the rules YAML file!");
-
+						Console.WriteLine($"Ignoring unknown actor type: `{kvp.Actor.ToLowerInvariant()}`");
+					else
+					{
 						var a = new ActorReference(kvp.Actor)
 						{
 							new LocationInit(locationOnMap),
@@ -402,6 +403,7 @@ namespace OpenRA.Mods.D2k.UtilityCommands
 					}
 				}
 			}
+		}
 
 		CPos GetCurrentTilePositionOnMap()
 		{