fix: Subtraction with underflow on empty FixedSizeBinaryArray

[DzenanJupic]

When trying to deserialize an arrow IPC stream with a fixed-size binary array that contains no values, the code currently subtracts with underflow. In the Python package (which uses a release build), this is silently ignored as debug assertions are turned off. Instead, you get a panic about an out-of-bounds offset.
PanicException: assertion failed: self.check_bound(offset)

By checking for an underflow, everything works fine.

To reproduce the issue, you can try the following code:

// [dependencies]
// arrow = "53.3.0"
// polars = { version = "1.16.0", features = ["polars-io", "ipc", "ipc_streaming"] }

use std::sync::Arc;
use arrow::{datatypes::{DataType, Field, Schema}, record_batch::RecordBatch};
use polars::io::{SerReader, ipc::IpcStreamReader};

fn main() {
    let mut buffer = Vec::new();

    let field = Field::new("bin", DataType::FixedSizeBinary(42), false);
    let schema = Arc::new(Schema::new(vec![field]));

    let column = Arc::new(arrow::array::FixedSizeBinaryBuilder::new(42).finish()) as _;
    let batch = RecordBatch::try_new(schema.clone(), vec![column]).unwrap();

    let mut writer = arrow::ipc::writer::StreamWriter::try_new(&mut buffer, &schema).unwrap();
    writer.write(&batch).unwrap();
    writer.finish().unwrap();

    let _ = IpcStreamReader::new(std::io::Cursor::new(&buffer[..]))
        .finish()
        .unwrap();
}

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes missing coverage. Please review.

Project coverage is 79.53%. Comparing base (58f763a) to head (a67f70c).
Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-compute/src/cast/binary_to.rs	42.85%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20109      +/-   ##
==========================================
- Coverage   79.53%   79.53%   -0.01%     
==========================================
  Files        1563     1563              
  Lines      217115   217116       +1     
  Branches     2464     2464              
==========================================
- Hits       172679   172677       -2     
- Misses      43876    43879       +3     
  Partials      560      560              

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