Schema mismatch caused by fold

[coastalwhite]

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 polars as pl

print(pl.Series([1]).to_frame().lazy().select(x = ~pl.fold(True, lambda acc, s: acc & s.is_null(), pl.all())).collect_schema())
print(pl.Series([1]).to_frame().lazy().select(x = ~pl.fold(True, lambda acc, s: acc & s.is_null(), pl.all())).collect())

Log output

Schema([('x', Int64)])

shape: (1, 1)
┌──────┐
│ x    │
│ ---  │
│ bool │
╞══════╡
│ true │
└──────┘

Issue description

There is a schema mismatch between collect_schema and collect.

Expected behavior

These are the same

Installed versions

Replace this line with the output of pl.show_versions(). Leave the backticks in place.

[coastalwhite]

A similar one that is more difficult to solve:

print(pl.Series([1], dtype=pl.Int32).to_frame().lazy().select(x = pl.fold(pl.Series([2], dtype=pl.Int8), lambda acc, s: acc + s, pl.all())).collect_schema())
# Int8

print(pl.Series([1], dtype=pl.Int32).to_frame().lazy().select(x = pl.fold(pl.Series([2], dtype=pl.Int8), lambda acc, s: acc + s, pl.all())).collect())
# Int32