Support multiple predictions

4aa0478d mistakenly broke the confidence score computation when predicting on multiple images at once.

dan/ocr/predict/prediction.py

@@ -339,7 +339,7 @@ def process_batch(
         # Return mean confidence score
         if confidence_score:
             result["confidences"] = {}
-            char_confidences = prediction["confidences"][0]
+            char_confidences = prediction["confidences"][idx]
             text = result["text"]
             start_tokens, end_tokens = zip(*list(tokens.values()))
             end_tokens = list(filter(bool, end_tokens))