improved search for visible view controller in navigation controller
improved search for visible view controller in navigation controller

0x73/JVMenuPopover,0x73/JVMenuPopover,mohsinalimat/JVMenuPopover,shenhzou654321/JVMenuPopover,JV17/JVMenuPopover,derekjcarter/JVMenuPopover,0x73/JVMenuPopover,ernestopino/JVMenuPopover