Bookmarks prev/next via gestures: add location to stack (#6306)

Was correctly done when jumping bookmarks via the Bookmarks
menu and the SkimTo widget, but not from gestures.
Also prevent fillToc() on each page turn when book has no TOC.

frontend/apps/reader/modules/readerbookmark.lua

@@ -647,12 +647,18 @@ function ReaderBookmark:onGotoNextBookmark(pn_or_xp)
     return true
 end
 
-function ReaderBookmark:onGotoNextBookmarkFromPage()
+function ReaderBookmark:onGotoNextBookmarkFromPage(add_current_location_to_stack)
+    if add_current_location_to_stack ~= false then -- nil or true
+        self.ui.link:addCurrentLocationToStack()
+    end
     self:gotoBookmark(self:getNextBookmarkedPageFromPage(self.ui:getCurrentPage()))
     return true
 end
 
-function ReaderBookmark:onGotoPreviousBookmarkFromPage()
+function ReaderBookmark:onGotoPreviousBookmarkFromPage(add_current_location_to_stack)
+    if add_current_location_to_stack ~= false then -- nil or true
+        self.ui.link:addCurrentLocationToStack()
+    end
     self:gotoBookmark(self:getPreviousBookmarkedPageFromPage(self.ui:getCurrentPage()))
     return true
 end

frontend/apps/reader/modules/readertoc.lua

@@ -79,7 +79,7 @@ function ReaderToc:onPosUpdate(pos, pageno)
 end
 
 function ReaderToc:fillToc()
-    if self.toc and #self.toc > 0 then return end
+    if self.toc then return end
     if self.ui.document:canHaveAlternativeToc() then
         if self.ui.doc_settings:readSetting("alternative_toc") then
             -- (if the document has a cache, the previously built alternative

frontend/apps/reader/skimtowidget.lua

@@ -412,7 +412,8 @@ end
 function SkimToWidget:goToByEvent(event_name)
     if event_name then
         self:addOriginToLocationStack()
-        self.ui:handleEvent(Event:new(event_name))
+        self.ui:handleEvent(Event:new(event_name, false))
+            -- add_current_location_to_stack=false, as we handled it here
         self.curr_page = self.ui:getCurrentPage()
         self:update()
     end