[examples/summarization] deal with None in data records (#14816)

* [examples/summarization] deal with None in data records

* rewrite to use a simpler (slower) variant

examples/pytorch/summarization/run_summarization.py

@@ -436,8 +436,14 @@ def main():
         )
 
     def preprocess_function(examples):
-        inputs = examples[text_column]
-        targets = examples[summary_column]
+
+        # remove pairs where at least one record is None
+        inputs, targets = [], []
+        for i in range(len(examples[text_column])):
+            if examples[text_column][i] is not None and examples[summary_column][i] is not None:
+                inputs.append(examples[text_column][i])
+                targets.append(examples[summary_column][i])
+
         inputs = [prefix + inp for inp in inputs]
         model_inputs = tokenizer(inputs, max_length=data_args.max_source_length, padding=padding, truncation=True)