fix: Reading Parquet with Null dictionary page

This fixes an issue with some Parquet writers that write dictionary pages for Null arrays (why?? I have no idea?).

Fixes pola-rs#18085.
Fixes pola-rs#18079.

Possibly also pola-rs#18061.

crates/polars-parquet/src/arrow/read/deserialize/null.rs

@@ -124,6 +124,8 @@ pub fn iter_to_arrays(
     data_type: ArrowDataType,
     mut filter: Option<Filter>,
 ) -> ParquetResult<Box<dyn Array>> {
+    _ = iter.read_dict_page()?;
+
     let num_rows = Filter::opt_num_rows(&filter, iter.total_num_values());
 
     let mut len = 0usize;

crates/polars-parquet/src/parquet/read/compression.rs

@@ -215,12 +215,14 @@ impl Iterator for BasicDecompressor {
             Some(Ok(p)) => p,
         };
 
-        Some(decompress(page, &mut self.buffer).map(|p| {
-            if let Page::Data(p) = p {
-                p
-            } else {
-                panic!("Found compressed page in the middle of the pages")
-            }
+        Some(decompress(page, &mut self.buffer).and_then(|p| {
+            let Page::Data(p) = p else {
+                return Err(ParquetError::oos(
+                    "Found dictionary page beyond the first page of a column chunk",
+                ));
+            };
+
+            Ok(p)
         }))
     }