fix exception

llm_server/database/database.py

@@ -143,7 +143,7 @@ def sum_column(table_name, column_name):
     try:
         cursor.execute(f"SELECT SUM({column_name}) FROM {table_name}")
         result = cursor.fetchone()
-        return result[0] if result[0] else 0
+        return result[0] if result else 0
     finally:
         cursor.close()