Skip NER level probability computation if there are no entities

dan/ocr/predict/attention.py

@@ -198,6 +198,9 @@ def split_text_and_confidences(
                 return [], [], []
 
             indices = build_ner_indices(text, tokens)
+            if not indices:
+                return [], [], []
+
             texts, confidences = compute_prob_by_ner(text, confidences, indices)
         case _:
             logger.error(f"Level should be either {list(map(str, Level))}")