.sink_parquet() sometimes panics when statistics has "null_count": False

[etiennebacher]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import os
os.environ["POLARS_VERBOSE"] = "1"
import polars as pl

test = pl.LazyFrame({"a": [1]})

test.sink_parquet("foo.parquet", statistics={"null_count": False, "min": True, "max": False, "distinct_count": True})

Log output

RUN STREAMING PIPELINE
[df -> parquet_sink]
thread '<unnamed>' panicked at crates/polars-pipe/src/executors/sinks/output/parquet.rs:47:33:
called `Result::unwrap()` on an `Err` value: ComputeError(ErrString("parquet: File out of specification: null count of a page is required"))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread '<unnamed>' panicked at crates/polars-pipe/src/executors/sinks/output/parquet.rs:127:14:
called `Result::unwrap()` on an `Err` value: Any { .. }
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/etienne/.local/lib/python3.10/site-packages/polars/_utils/unstable.py", line 58, in wrapper
    return function(*args, **kwargs)
  File "/home/etienne/.local/lib/python3.10/site-packages/polars/lazyframe/frame.py", line 2233, in sink_parquet
    return lf.sink_parquet(
pyo3_runtime.PanicException: called `Result::unwrap()` on an `Err` value: Any { .. }

Issue description

sink_parquet() panics when null_count is False in the argument statistics, but only when other values of statistics are provided. For example, this works:

test.sink_parquet("foo.parquet", statistics={"null_count": False})

but this panics:

test.sink_parquet("foo.parquet", statistics={"null_count": False, "min": True, "max": False, "distinct_count": True})

Expected behavior

Should work or give a proper error instead of panicking.

Installed versions

--------Version info---------
Polars:               1.0.0-rc.2
Index type:           UInt32
Platform:             Linux-6.5.0-41-generic-x86_64-with-glibc2.35
Python:               3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               <not installed>
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               <not installed>
matplotlib:           <not installed>
nest_asyncio:         <not installed>
numpy:                1.21.5
openpyxl:             <not installed>
pandas:               <not installed>
pyarrow:              <not installed>
pydantic:             <not installed>
pyiceberg:            <not installed>
sqlalchemy:           <not installed>
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[etiennebacher]

This produces a proper error for write_parquet():

import os
os.environ["POLARS_VERBOSE"] = "1"
import polars as pl

test = pl.DataFrame({"a": [1]})

test.write_parquet("foo.parquet", statistics={"null_count": False, "min": True, "max": False, "distinct_count": True})

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/etienne/.local/lib/python3.10/site-packages/polars/dataframe/frame.py", line 3554, in write_parquet
    self._df.write_parquet(
polars.exceptions.ComputeError: parquet: File out of specification: null count of a page is required