parse arg being empty string to be false

Signed-off-by: HuiyingLi <willwin.lee@gmail.com>

tests/export/nemo_export.py

@@ -784,6 +784,8 @@ def str_to_bool(name: str, s: str, optional: bool = False) -> Optional[bool]:
  s = s.lower()
  true_strings = ["true", "1"]
  false_strings = ["false", "0"]
+ if s == '':
+ return False
  if s in true_strings:
  return True
  if s in false_strings: