Widgetset Compilation Failed: NullPointerException

I have been working on this Vaadin project for a few days now with no problems. And now, it cannot compile the widgset. I am very new to Vaadin so I have no clue why this is happening. I read around for similar problems and the only possible solution I could find was to add Vaadin as a project facet. I did that and it did not work. It is not giving me any further details in the error log either. Any idea on what could be causing this? Any and all help would be very appreciated.