fix bug when layout_predictor is None

[GreatV]

from paddleocr import PPStructure

table_ocr = PPStructure(
    use_pdserving=False, use_gpu=False, lang="en", layout=False, show_log=False
)

result = table_ocr(
    "./data/paddle.png", return_ocr_result_in_table=True
)

  File "/Users/wangxin/repos/PaddleOCR/paddleocr.py", line 855, in __call__
    res, _ = super().__call__(img, return_ocr_result_in_table, img_idx=img_idx)
  File "/Users/wangxin/repos/PaddleOCR/ppstructure/predict_system.py", line 172, in __call__
    "score": region["score"],
KeyError: 'score'

• add layout score return #13068

[UserWangZz]

LGTM