[fix](parquet) the key colum of map type in parquet may be nullable (#23180)
Fix errors when reading map type with nullable key column in parquet file. `ParquetReader` support to read nullable key column, but add a check to prevent reading nullable key column. Unfortunately, this check error was not thrown correctly, causing the BE to crash, and thrown meaningless error logs in be.out:
```
...
11# doris::vectorized::ParquetReader::get_columns(std::unordered_map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, doris::TypeDescriptor, std::hash<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::equal_to<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, doris::TypeDescriptor> > >*, std::unordered_set<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::hash<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::equal_to<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >*) at /root/doris/be/src/vec/exec/format/parquet/vparquet_reader.cpp:508
12# doris::vectorized::VFileScanner::_get_next_reader() in /root/yun_you_external/output/be/lib/doris_be
13# doris::vectorized::VFileScanner::_get_block_impl(doris::RuntimeState*, doris::vectorized::Block*, bool*) at /root/doris/be/src/vec/exec/scan/vfile_scanner.cpp:241
...
```
4bf055c818