Calling planner-create-task-from-buffer breaks emacs-wiki:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  replace-regexp-in-string("\\]" "%5D" nil t t)
  emacs-wiki-replace-regexp-in-string("\\]" "%5D" nil)
  emacs-wiki-link-escape("E-Mail from auto-confirm@amazon.com" t)
  emacs-wiki-make-link("gnus://nnimap+localhost:INBOX.mail/<.AAA-notify-27691,3139.1126382393@us-bdb-2102.iad2.amazon.com>" "E-Mail from auto-confirm@amazon.com")
  (if (or (null link) (string= link "")) "" (emacs-wiki-make-link link name))
  planner-make-link("gnus://nnimap+localhost:INBOX.mail/<.AAA-notify-27691,3139.1126382393@us-bdb-2102.iad2.amazon.com>" "E-Mail from auto-confirm@amazon.com" t)
  (let ((articles ...)) (planner-make-link (concat "gnus://" gnus-newsgroup-name "/" ...) (if ... ... ...) t))
  (progn (let (...) (planner-make-link ... ... t)))
  (if (equal major-mode (quote gnus-summary-mode)) (progn (let ... ...)))
  (when (equal major-mode (quote gnus-summary-mode)) (let (...) (planner-make-link ... ... t)))
  planner-gnus-annotation-from-summary()
  (or (planner-gnus-annotation-from-summary) (planner-gnus-annotation-from-message))
  planner-gnus-annotation()
  run-hook-with-args-until-success(planner-gnus-annotation)
  (let ((planner-create-task-hook ...) (annotation ...)) (when (and planner-annotation-symbol-string ...) (setq title ... annotation nil)) (planner-create-task title (when ... date) annotation plan-page status))
  planner-create-task-from-buffer("Learn [[Planner]] create from buffer function." nil "Planner" "_")

• call-interactively(planner-create-task-from-buffer)

  execute-extended-command(nil)
  call-interactively(execute-extended-command)

Here is a fix:

--- orig/emacs-wiki.el
+++ mod/emacs-wiki.el
@@ -1069,7 +1069,7 @@
        "\\[" "%5B"
        (emacs-wiki-replace-regexp-in-string
         "\\]" "%5D"
-        (unless is-desc
+        (if is-desc ""
           (emacs-wiki-replace-regexp-in-string
            " " "%20" text)))))))