Update run_squad.py

Indentation change so that the output "nbest_predictions.json" is not empty.

examples/run_squad.py

@@ -617,7 +617,7 @@ def write_predictions(all_examples, all_features, all_results, n_best_size,
                 all_predictions[example.qas_id] = ""
             else:
                 all_predictions[example.qas_id] = best_non_null_entry.text
-            all_nbest_json[example.qas_id] = nbest_json
+        all_nbest_json[example.qas_id] = nbest_json
 
     with open(output_prediction_file, "w") as writer:
         writer.write(json.dumps(all_predictions, indent=4) + "\n")