Clarified exceptions when using NodeById and MediaById and passing empty strings, e.g. if your source came from @Parameter

umbraco.MacroEngines.Juno/RazorDynamicNode/RazorLibraryCore.cs

@@ -60,6 +60,7 @@ namespace umbraco.MacroEngines.Library
             {
                 return MediaById(mediaId);
             }
+            throw new ArgumentException("Cannot get MediaById without an id");
             return null;
         }
         public DynamicNode MediaById(object Id)