ignore single file for tsp folder file check (#483)

Author: AllyW

src/aaz_dev/swagger/model/specs/_typespec_helper.py

@@ -33,6 +33,8 @@ def find_mgmt_plane_entry_files(cls, folder):
     @classmethod
     def find_data_plane_entry_files(cls, folder):
         files = []
+        if not os.path.isdir(folder):
+            return files
         for ts_path, cfg_path in cls._iter_entry_files(folder):
             namespace, is_mgmt_plane = cls._parse_main_tsp(ts_path)
             if not namespace: