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GH-31992: [C++][Parquet] Handling the special case when DataPageV2 values buffer is empty (#45252)



### Rationale for this change

In DataPageV2, the levels and data will not be compressed together. So, we might get the "empty" data page buffer.

When meeting this, Snappy C++ will failed to decompress the `(input_len == 0, output_len == 0)` data.

### What changes are included in this PR?

Handling the case in `column_reader.cc`

### Are these changes tested?

* [x] Will add

### Are there any user-facing changes?

Minor fix

* GitHub Issue: #31992

Lead-authored-by: mwish <maplewish117@gmail.com>
Co-authored-by: mwish <1506118561@qq.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Signed-off-by: mwish <maplewish117@gmail.com>