Steps to reproduce this bug:
1. Open the context menu for the the search field and select "Add keyword for search" (may have other wording, I only have a German Browser).
2. Enter name and keyword and click "OK".
3. Enter the keyword and a word you want to search for in the address bar of Firefox.
Search result page
"Page not found".
This error occurs because there is an empty "id" parameter in the action attribute of the search form tag.
Use DOKU_SCRIPT instead of wl() in tpl_searchform. (See attached patch.)