BFilePanel with B_DIRECTORY_NODE allows file selection

[kallisti5]

Per the documentation: ​https://www.haiku-os.org/legacy-docs/bebook/BFilePanel_Overview.html#BFilePanel_Constructing_Fine_Tuning

If the setting includes B_DIRECTORY_NODE and the user selects and
Opens (i.e. clicks the Open button) a directory or a symlink to
a directory, the directory (or symlink) is delivered to your
target. If it doesn't include B_DIRECTORY_NODE and the user Opens
a directory (or symlink to a directory), the directory is entered
(the contents of the directory are displayed in the file list).

Specifying B_DIRECTORY_NODE only results in a BFilePanel which can:

• Open directories.
• Open files if you double-click them

Given the documentation, one would expect B_DIRECTORY_NODE without B_FILE_NODE to not allow users to select files.

[kallisti5]

EDIT: Clarified description. This only occurs if you "double click" files in the BFilePane to select them. Clicking OK blocks your attempt to open.

I feel like the correct solution would be to just hide non-directories when B_DIRECTORY_NODE is the setting.