Fixed bug when closing window with other page resources and in clear command

[bjhoohaha]

Clear command in Itinerary page not behaving as should

typing clear multiple times produce many windows that may not be the correct behaviour

Bug where error is shown when exiting application before clear window is closed:

goto itinerary

switch to itinerary window

clear

clear window shows up and before clicking proceed, exit application

exit

error message shows up on intellij

Bug where error is shown when page resources are not closed when exiting application:

goto address_book

navigate to address book

click help

opens up help window

goto main

navigate to main

exit application by clicking X on window

error message shows up on intelllij

Application's help and code window is not behaving as should

Current application allows the user to open 5 help windows. The application should close all resources in the current page before moving on to get the next page.

[pohlinwei]

Overall, I think that it can be merged (: