add calling item.callback() as default onMenuChoice action

frontend/ui/menu.lua

@@ -480,9 +480,13 @@ function Menu:onMenuSelect(item)
 end
 
 --[[
-override this function to handle the choice
+	default to call item callback
-]]--
+	override this function to handle the choice
+--]]
 function Menu:onMenuChoice(item)
+	if item.callback then
+		item.callback()
+	end
 	return true
 end
 

frontend/ui/reader/readerfont.lua

@@ -99,11 +99,6 @@ function ReaderFont:onShowFontMenu()
 		item_table = self.face_table,
 		width = Screen:getWidth() - 100,
 	}
-	function main_menu:onMenuChoice(item)
-		if item.callback then
-			item.callback()
-		end
-	end
 	-- build container
 	local menu_container = CenterContainer:new{
 		main_menu,

frontend/ui/reader/readermenu.lua

@@ -73,11 +73,6 @@ function ReaderMenu:onShowMenu()
 		item_table = self.item_table,
 		width = Screen:getWidth() - 100,
 	}
-	function main_menu:onMenuChoice(item)
-		if item.callback then
-			item.callback()
-		end
-	end
 
 	local menu_container = CenterContainer:new{
 		ignore = "height",