Cleanup get_vlen_bytes_and_offsets

src/array/codec/array_to_bytes/vlen.rs

@@ -92,19 +92,27 @@ fn get_vlen_bytes_and_offsets(
         }
         _ => unreachable!("other data types are not part of VlenIndexDataType"),
     };
-    let data_len_expected = *index.last().unwrap();
+
+    // Get the data length
+    let Some(&data_len_expected) = index.last() else {
+        return Err(CodecError::Other(
+            "Index is empty? It should have at least one element".to_string(),
+        ));
+    };
 
     // Decode the data
     let data = &bytes[data_start..data_start + data_compressed_len];
     let data = if let Ok(data_len_expected) = NonZeroU64::try_from(data_len_expected as u64) {
         data_codecs.decode(
             data.into(),
-            &ChunkRepresentation::new(
-                vec![data_len_expected],
-                DataType::UInt8,
-                FillValue::from(0u8),
-            )
-            .unwrap(),
+            &unsafe {
+                // SAFETY: data type and fill value are compatible
+                ChunkRepresentation::new_unchecked(
+                    vec![data_len_expected],
+                    DataType::UInt8,
+                    FillValue::from(0u8),
+                )
+            },
             options,
         )?
     } else {
@@ -114,12 +122,14 @@ fn get_vlen_bytes_and_offsets(
     .into_owned();
     let data_len = data.len();
 
-    // Validate the offsets
+    // Check the data length is as expected
     if data_len != data_len_expected {
         return Err(CodecError::Other(format!(
             "Expected data length {data_len_expected} does not match data length {data_len}"
         )));
     }
+
+    // Validate the offsets
     for (curr, next) in index.iter().tuple_windows() {
         if next < curr || *next > data_len {
             return Err(CodecError::Other(