Doing a text agenda search with org-agenda-text-search-extra-files set to (agenda-archives) and with a buffer restriction results in an error:
Debugger entered--Lisp error: (wrong-type-argument stringp agenda-archives) file-exists-p(agenda-archives) #[(a b) "\302 !\205 \302 !\205 \303 \"\207" [a b file-exists-p file-equal-p] 3]("/tmp/tmp.org" agenda-archives) cl--position("/tmp/tmp.org" (agenda-archives) 0 1) cl--delete-duplicates(("/tmp/tmp.org" agenda-archives) (:test #[(a b) "\302 !\205 \302 !\205 \303 \"\207" [a b file-exists-p file-equal-p] 3]) t) cl-remove-duplicates(("/tmp/tmp.org" agenda-archives) :test #[(a b) "\302 !\205 \302 !\205 \303 \"\207" [a b file-exists-p file-equal-p] 3]) org-search-view(nil) funcall-interactively(org-search-view nil) call-interactively(org-search-view) org-agenda(nil) funcall-interactively(org-agenda nil) call-interactively(org-agenda nil nil) command-execute(org-agenda) Emacs : GNU Emacs 25.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.26) of 2017-12-04 Package: Org mode version 9.1.5 (9.1.5-1-gb3ddb0-elpaplus @ /home/ionasal/.emacs.d/elpa/org-plus-contrib-20171225/)