Refresh sample10 metric JSON exports to null

artifacts/results/metric_iter31_sample10_all_metrics_verify/episode43/episode43.metrics.json

@@ -11,10 +11,10 @@
   "retrieve_cross_frame": -1,
   "ready_cross_frame": 226,
   "ordering_ok": true,
-  "dense_boundary_error_to_retrieve_frames": NaN,
+  "dense_boundary_error_to_retrieve_frames": null,
   "dense_boundary_error_frames": 79.0,
   "dense_boundary_error_fraction": 0.26421404682274247,
-  "key_boundary_error_to_retrieve_keyframes": NaN,
+  "key_boundary_error_to_retrieve_keyframes": null,
   "key_boundary_error_keyframes": 1.0,
   "auroc_vret_ypre_three": 0.8824624624624624,
   "auprc_vret_ypre_three": 0.8701576807166871,
@@ -24,9 +24,9 @@
   "auprc_ppre_ypre": 1.0,
   "auroc_pext_yext": 1.0,
   "auprc_pext_yext": 1.0,
-  "auroc_phase_yretrieve": NaN,
-  "auprc_phase_yretrieve": NaN,
-  "f1_phase_yretrieve": NaN,
+  "auroc_phase_yretrieve": null,
+  "auprc_phase_yretrieve": null,
+  "f1_phase_yretrieve": null,
   "auroc_phase_yready": 0.997787610619469,
   "auprc_phase_yready": 0.9864864864864865,
   "f1_phase_yready": 0.648888888888889,