Fixed UnboundLocalError for empty preds_str in recognizer_predict

[RUTUPARNk]

🐞 Bug Fix: Handle UnboundLocalError in recognizer_predict

This patch ensures that preds_str and preds_max_prob are always initialized before use in recognizer_predict().

Previously, calling .readtext() on certain decoders (e.g., Tesseract or empty input) led to: UnboundLocalError: cannot access local variable 'preds_str'

Fixes #1415