show_additional_headers plugin shows "Array" when using threaded list view

[thomask77]

Hi!

I'm using the show_additional_headers plugin, and configured it to show the X-Original-To header:

$config['identity_select_headers'] = ['X-Original-To']; 

When the List mode is set to "List", everything works fine. For example, it shows "mail+github@t-kindler.de".

But when the list mode is set to "Threads", it shows "Array" instead of the correct header contents.
(All other built-in headers are showing up fine).

[alecpl]

I guess it's show_additional_headers, not identity_select_headers ;)

Anyway, I confirm that if the header exists multiple times in the message "Array" is displayed. It has nothing to do with list mode.

[alecpl]

Fixed.