Reading an Enum from csv raises a StringCache error

[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

with pl.StringCache():
    csv_data = pl.DataFrame({
        "someletter": ["A", "B"]
    })
    csv_data.write_csv("example.csv")
 
    schema = pl.Schema({
        "someletter": pl.Enum(["A", "B"]),
    })
    pl.scan_csv("example.csv", schema=schema).sink_parquet("example.parquet")

Log output

Issue description

StringCacheError.

Expected behavior

No error.

Installed versions

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