Update NST.py

NST.py

@@ -268,7 +268,7 @@ class Nst(datasets.GeneratorBasedBuilder):
                                 fields["age"] = fields["age"].strip().split(" ")[0].strip()
                             if fields["age"].lower() in ("slethei", "ramslie") or not fields["age"].strip():
                                 fields["age"] = 0
-                            for int32_field in ("number_of_recordings", "recording_session", "sheet_number", "channels", "frequency", "t0", "t1", "t2"):
+                            for int32_field in ("number_of_recordings", "recording_session", "sheet_number", "channels", "t0", "t1", "t2"):
                                 if not fields[int32_field].strip():
                                     fields[int32_field] = 0
                             yield metadata_key, {