Improperly fixing some NULL pointer conversion warnings
Merge branch 'feature/warningfix-NULL-conversions' into merge-test

* feature/warningfix-NULL-conversions:
  Improperly fixing some NULL pointer conversion warnings

Conflicts:
	Samples/invaders/src/DecoratorDefender.cpp
	Samples/tutorial/datagrid/src/DecoratorDefender.cpp
	Samples/tutorial/datagrid_tree/src/DecoratorDefender.cpp