Fix error while optimizing ruleset when no judge area is defined.

Assets/Cryville/Crtr/Ruleset.cs

@@ -44,7 +44,7 @@ namespace Cryville.Crtr {
 					etor.Optimize(e.Value);
 				}
 			}
-			foreach (var a in areas) {
+			if (areas != null) foreach (var a in areas) {
 				etor.Optimize(a.Value);
 			}
 			foreach (var j in judges) {