don't break apart when using empty IReadOnlyDictionary

OpenRA.Game/FieldSaver.cs

@@ -82,6 +82,9 @@ namespace OpenRA
 				return elems.JoinWith(", ");
 			}
 
+			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(OpenRA.Primitives.Cache<,>))
+				return ""; // TODO
+
 			if (t == typeof(DateTime))
 				return ((DateTime)v).ToString("yyyy-MM-dd HH-mm-ss", CultureInfo.InvariantCulture);
 

OpenRA.Utility/Command.cs

@@ -257,6 +257,9 @@ namespace OpenRA.Utility
 			if (t.IsSubclassOf(typeof(Array)))
 				return "Multiple {0}".F(FriendlyTypeName(t.GetElementType()));
 
+			if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(OpenRA.Primitives.Cache<,>))
+				return "Cached<{0},{1}>".F(t.GetGenericArguments().Select(FriendlyTypeName).ToArray());
+
 			if (t == typeof(int) || t == typeof(uint))
 				return "Integer";