Unable to get result from an IFileOpenDialog's IShellItem#get_display_name

[cyberarm]

require "win32cr"
require "win32cr/system/com"

LibWin32.CoInitializeEx(nil, LibWin32::COINIT::COINIT_APARTMENTTHREADED | LibWin32::COINIT::COINIT_DISABLE_OLE1DDE)

begin
  com = ComPtr(LibWin32::IFileOpenDialog).new(LibWin32::CLSID_FileOpenDialog, LibWin32::IID_IFileOpenDialog)
  default_flags = 0_u32
  com.get_options(pointerof(default_flags))
  com.set_options((default_flags | LibWin32::FILEOPENDIALOGOPTIONS::FOS_PATHMUSTEXIST.to_i | LibWin32::FILEOPENDIALOGOPTIONS::FOS_PICKFOLDERS.to_i))
  com.show(Pointer(Void).null)

  item = LibWin32::IShellItem.new
  buffer = uninitialized UInt16*
  if com.get_folder(pointerof(item))
    result = item.get_display_name(pointerof(item), LibWin32::SIGDN::SIGDN_FILESYSPATH, pointerof(buffer))
    pp result #String.from_utf16(buffer)
    # pp String.from_utf16(buffer)[0]
  else
    puts "Failed."
  end
rescue e
  puts e.message
end

LibWin32.CoUninitialize

Invalid memory access (C0000005) at address 0x7fffe5785de8
[0x7fffe5785de8] ShellExecuteExW +759464 in C:\Windows\SYSTEM32\windows.storage.dll
[0x7ff6a8c50cc1] get_display_name at C:\Users\cyber\Code\w3dhub_packager_webview\lib\win32cr\src\win32cr\ui\shell.cr:17422
[0x7ff6a8b8177e] __crystal_main at C:\Users\cyber\Code\w3dhub_packager_webview\src\w3dhub_packager.cr:16
[0x7ff6a8c57569] main_user_code at C:\Users\cyber\Applications\crystal-1.12.1\src\crystal\main.cr:129
[0x7ff6a8c5748a] main at C:\Users\cyber\Applications\crystal-1.12.1\src\crystal\main.cr:115
[0x7ff6a8bcf449] main at C:\Users\cyber\Applications\crystal-1.12.1\src\crystal\main.cr:141
[0x7ff6a8bcf563] wmain at C:\Users\cyber\Applications\crystal-1.12.1\src\crystal\system\win32\wmain.cr:37
[0x7ff6a8c58da0] __scrt_common_main_seh at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
[0x7fffe7cb7344] BaseThreadInitThunk +20 in C:\Windows\System32\KERNEL32.DLL
[0x7fffe9ae26b1] RtlUserThreadStart +33 in C:\Windows\SYSTEM32\ntdll.dll

Function being used:
https://github.com/mjblack/win32cr/blob/c4da22cfbe3bf363bf7ef5af1c00408f6626ce42/src/win32cr/ui/shell.cr#L17421-L17423

  def get_display_name(this : IShellItem*, sigdnname : SIGDN, ppszname : LibC::LPWSTR*) : HRESULT
    @lpVtbl.value.get_display_name.call(this, sigdnname, ppszname)
  end

*it is midnight, so I may be missing something obvious...