degesch: create servers from configuration

This means that as of now, the only way of creating a server is
to edit the configuration file by hand and add (at least) an empty
object under the server's name.

common.c

@@ -1131,7 +1131,6 @@ config_schema_accepts_type
 	 && config_item_type_is_string (type))
 		return true;
 	return !self->default_ && type == CONFIG_ITEM_NULL;
-
 }
 
 static bool
@@ -2008,6 +2007,7 @@ config_load (struct config *self, struct config_item_ *root)
 			subtree = config_item_object ();
 			str_map_set (&root->value.object, module->name, subtree);
 		}
-		module->loader (subtree, module->user_data);
+		if (module->loader)
+			module->loader (subtree, module->user_data);
 	}
 }