The search field value on the main page of bukuserver isn't always submitted on search

[LeXofLeviafan]

The search form on the main page of bukuserver includes two checkboxes ("Deep search" & "Regex"), a text field ("Keyword") and the submit button ("Search"). When either (or both) of the checkboxes are set, submitting the form (whether by clicking the button or by hitting Enter) opens the bookmark/ page with the textfield value passed as a corresponding parameter (such as ?flt1_buku_search_regex=, ?flt2_buku_search_deep= or ?flt3_buku_search_deep_regex=), resulting in a page with corresponding filter ("buku: search regex", "buku: search deep" or "buku: search deep, regex").

Given that, one would assume that submitting the form without setting either checkbox would result in a page with "buku: search" filter (?flt2_buku_search=); however, what I'm getting instead is a regular bookmark/ page without parameters (and thus without any filters).