PASTE CODE HERE
```smallbaselineApp.py 


**Full error message**
Traceback (most recent call last):
  File "/home/bzhang64/.conda/envs/isce2_py38/bin/smallbaselineApp.py", line 8, in <module>
    sys.exit(main())
  File "/home/bzhang64/MintPy/mintpy/cli/smallbaselineApp.py", line 208, in main
    run_smallbaselineApp(inps)
  File "/home/bzhang64/MintPy/mintpy/smallbaselineApp.py", line 1114, in run_smallbaselineApp
    app.open()
  File "/home/bzhang64/MintPy/mintpy/smallbaselineApp.py", line 79, in open
    self._read_template()
  File "/home/bzhang64/MintPy/mintpy/smallbaselineApp.py", line 132, in _read_template
    out_file = os.path.join(backup_dir, os.path.basename(tfile))
  File "/home/bzhang64/.conda/envs/isce2_py38/lib/python3.8/posixpath.py", line 142, in basename
    p = os.fspath(p)
TypeError: expected str, bytes or os.PathLike object, not NoneType

**System information**

* Operating system: <!--Linux-CentOS,. -->
* Python environment: <!-- conda, -->
* MintPy version: <!-- MintPy version 1.4.1-20, -->
* Your custom / default template file (if the bug is related to a specific dataset): <!-- It helps the diagnose a lot if you could post the configurations you used. You can drag-and-drop them here directly. -->
[template.txt](https://github.com/insarlab/MintPy/files/9862744/template.txt)