[BUG] For certain parquet list schemas, the root PageNestingInfo struct can end up uninitialized.

Inside of the `allocate_nesting_info` function, we allocate PageNestingInfo and PageNestingDecodeInfo structs and initialize them. However, the logic for traversing the schema in the file can sometimes leave the 0th element uninitialized. This is a mild bug that leads to a slightly wrong size calculating for output chunk sizes in the chunked reader.

The easiest way to repro is with the file `python/cudf/cudf/tests/data/parquet/one_level_list.parquet`