Tweak IPathSearch to avoid exposing the OpenQueue directly.

OpenRA.Mods.Common/Traits/World/PathFinder.cs

@@ -121,7 +121,7 @@ namespace OpenRA.Mods.Common.Traits
 
 			List<CPos> path = null;
 
-			while (!search.OpenQueue.Empty)
+			while (search.CanExpand)
 			{
 				var p = search.Expand();
 				if (search.IsTarget(p))
@@ -156,7 +156,7 @@ namespace OpenRA.Mods.Common.Traits
 				fromDest.Debug = true;
 			}
 
-			while (!fromSrc.OpenQueue.Empty && !fromDest.OpenQueue.Empty)
+			while (fromSrc.CanExpand && fromDest.CanExpand)
 			{
 				// make some progress on the first search
 				var p = fromSrc.Expand();