Fix empty rows bug with training spreadsheet

src/npc_lims/status/behavior_sessions.py

@@ -100,6 +100,7 @@ def get_sessions_from_training_db() -> dict[int, tuple[dict[str, Any], ...]]:
                 for row in db.execute(
                     f"SELECT * FROM '{subject}' WHERE ignore != 1"
                 ).fetchall()
+                if row['start_time'] # ie not empty
             )
     return sessions