reverse book_title part

plugins/vocabbuilder.koplugin/main.lua

@@ -77,14 +77,7 @@ local function resetButtonOnLookupWindow()
                 text = _("Add to vocabulary builder"),
                 font_bold = false,
                 callback = function()
-                    local book_title = obj.ui.doc_settings and obj.ui.doc_settings:readSetting("doc_props").title or _("Dictionary lookup")
-                    if book_title == "" then -- no or empty metadata title
-                        if obj.ui.document and obj.ui.document.file then
-                            local util = require("util")
-                            local directory, filename = util.splitFilePathName(obj.ui.document.file) -- luacheck: no unused
-                            book_title = util.splitFileNameSuffix(filename)
-                        end
-                    end
+                    local book_title = (obj.ui.doc_props and obj.ui.doc_props.display_title) or _("Dictionary lookup")
                     obj.ui:handleEvent(Event:new("WordLookedUp", obj.word, book_title, true)) -- is_manual: true
                     local button = obj.button_table.button_by_id["vocabulary"]
                     if button then