Harder check for IndexErrors in QA scripts (#15438)

* Harder check for IndexErrors in QA scripts

* Make test stronger

examples/flax/question-answering/utils_qa.py

@@ -137,7 +137,9 @@ def postprocess_qa_predictions(
                         start_index >= len(offset_mapping)
                         or end_index >= len(offset_mapping)
                         or offset_mapping[start_index] is None
+                        or len(offset_mapping[start_index]) < 2
                         or offset_mapping[end_index] is None
+                        or len(offset_mapping[end_index]) < 2
                     ):
                         continue
                     # Don't consider answers with a length that is either < 0 or > max_answer_length.
@@ -147,6 +149,7 @@ def postprocess_qa_predictions(
                     # provided).
                     if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
                         continue
+
                     prelim_predictions.append(
                         {
                             "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),

examples/pytorch/question-answering/utils_qa.py

@@ -137,7 +137,9 @@ def postprocess_qa_predictions(
                         start_index >= len(offset_mapping)
                         or end_index >= len(offset_mapping)
                         or offset_mapping[start_index] is None
+                        or len(offset_mapping[start_index]) < 2
                         or offset_mapping[end_index] is None
+                        or len(offset_mapping[end_index]) < 2
                     ):
                         continue
                     # Don't consider answers with a length that is either < 0 or > max_answer_length.
@@ -147,6 +149,7 @@ def postprocess_qa_predictions(
                     # provided).
                     if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
                         continue
+
                     prelim_predictions.append(
                         {
                             "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),

examples/tensorflow/question-answering/utils_qa.py

@@ -137,7 +137,9 @@ def postprocess_qa_predictions(
                         start_index >= len(offset_mapping)
                         or end_index >= len(offset_mapping)
                         or offset_mapping[start_index] is None
+                        or len(offset_mapping[start_index]) < 2
                         or offset_mapping[end_index] is None
+                        or len(offset_mapping[end_index]) < 2
                     ):
                         continue
                     # Don't consider answers with a length that is either < 0 or > max_answer_length.
@@ -147,6 +149,7 @@ def postprocess_qa_predictions(
                     # provided).
                     if token_is_max_context is not None and not token_is_max_context.get(str(start_index), False):
                         continue
+
                     prelim_predictions.append(
                         {
                             "offsets": (offset_mapping[start_index][0], offset_mapping[end_index][1]),