array_min / array_max fail on a zero-row batch for non-primitive element types #26072

Describe the bug

array_min / array_max on a zero-row List<Utf8> (or any non-primitive element type) fails:

Execution error: Empty iterator passed to ScalarValue::iter_to_array

A zero-row List<Int64> works. array_min_max_helper (datafusion/functions-nested/src/min_max.rs) only has a fast path for primitive types; the fallback builds a Vec<ScalarValue> and calls ScalarValue::iter_to_array, which rejects an empty iterator.

Zero-row batches do reach these functions in practice: ProjectionExec and TopK evaluate expressions on every batch, so ORDER BY array_min(tags) LIMIT n fails whenever an input emits an empty batch.

To Reproduce

use std::sync::Arc;
use datafusion::arrow::array::{ArrayRef, ListBuilder, StringBuilder};
use datafusion::arrow::record_batch::RecordBatch;
use datafusion::prelude::SessionContext;

#[tokio::main]
async fn main() -> datafusion::error::Result<()> {
    let ctx = SessionContext::new();
    let tags: ArrayRef = Arc::new(ListBuilder::new(StringBuilder::new()).finish());
    ctx.register_batch("t", RecordBatch::try_from_iter(vec![("tags", tags)])?)?;
    ctx.sql("SELECT array_min(tags) FROM t").await?.show().await?; // error
    Ok(())
}

Seen on 54.0.0; the code is unchanged on main.

Expected behavior

Zero rows, the same as for primitive element types.

Additional context

Found in OpenSearch's DataFusion backend when sorting on multi-valued keyword fields with an empty shard. Proposed fix: return new_empty_array(&array.value_type()) for an empty input before the fallback. PR to follow.