panic when executing sql expression with invalid column

[ZemanOndrej]

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

    #[test]
    fn polars_panic() {
        let mut ctx = SQLContext::new();
        let df = df! {
            "col_1"=> ["1", "2", "3"],
        }
        .unwrap();
        ctx.register("df1", df.lazy());

        let res = ctx.execute("select * from df1 where nonexistent_col = 2"); // this is fine and returns Ok(Err(...))
        assert!(res.unwrap().collect().is_err());
        let res = ctx.execute("select * from df1 where nonexistent_col = '2'"); // this panics
        assert!(res.unwrap().collect().is_err());
    }

Log output

thread 'builtin::tests::polars_panic' panicked at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:389:88:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: rust_begin_unwind
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:665:5
   1: core::panicking::panic_fmt
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/panicking.rs:74:14
   2: core::panicking::panic
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/panicking.rs:148:5
   3: core::option::unwrap_failed
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/option.rs:2020:5
   4: core::option::Option<T>::unwrap
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/option.rs:970:21
   5: polars_sql::sql_expr::SQLExprVisitor::convert_temporal_strings::{{closure}}
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:389:40
   6: core::option::Option<T>::unwrap_or_else
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/option.rs:1015:21
   7: polars_sql::sql_expr::SQLExprVisitor::convert_temporal_strings
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:388:34
   8: polars_sql::sql_expr::SQLExprVisitor::visit_binary_op
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:469:15
   9: polars_sql::sql_expr::SQLExprVisitor::visit_expr
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:104:54
  10: polars_sql::sql_expr::parse_sql_expr
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/sql_expr.rs:1020:5
  11: polars_sql::context::SQLContext::process_where
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:871:41
  12: polars_sql::context::SQLContext::execute_select
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:645:14
  13: polars_sql::context::SQLContext::process_query
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:313:45
  14: polars_sql::context::SQLContext::execute_query_no_ctes
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:217:18
  15: polars_sql::context::SQLContext::execute_query
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:213:9
  16: polars_sql::context::SQLContext::execute_statement
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:196:40
  17: polars_sql::context::SQLContext::execute
             at /home/ubuntu/.cargo/registry/src/index.crates.io-6f17d22bba15001f/polars-sql-0.43.1/src/context.rs:158:19
  18: polars_poc::builtin::tests::polars_panic
             at ./src/builtin.rs:67:19
  19: polars_poc::builtin::tests::polars_panic::{{closure}}
             at ./src/builtin.rs:57:22
  20: core::ops::function::FnOnce::call_once
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/ops/function.rs:250:5
  21: core::ops::function::FnOnce::call_once
             at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Issue description

running that execute panics in /polars-sql-0.43.1/src/sql_expr.rs on line 389 when you try to unwrap None value

Expected behavior

the expected result of the execute function should be something like
Err(Context { error: Context { error: ColumnNotFound(ErrString("unable to find column \"nonexistent_col\"; valid columns: [\"col_1\"]")), msg: ErrString("'filter' failed") }, msg: ErrString("'select' input failed to resolve") })

Installed versions

polars = { version = "0.43.1", default-features = false, optional = false, features = [
"ipc_streaming",
"lazy",
"fmt",
"parquet",
"sql",
] }

[cmdlineluser]

Python repro.

pl.DataFrame({"a": [1]}).sql("select * from self where b = '2'")
# thread '<unnamed>' panicked at crates/polars-sql/src/sql_expr.rs:389:88:
# called `Option::unwrap()` on a `None` value

[ritchie46]

@alexander-beedie can you take a look?