MissionManager: Change NULL or 0 to nullptr

src/MissionManager/CameraCalc.h

src/MissionManager/CameraCalcTest.cc

src/MissionManager/CameraSection.cc

src/MissionManager/CameraSection.h

src/MissionManager/CameraSectionTest.cc

src/MissionManager/CameraSpec.h

src/MissionManager/CorridorScanComplexItem.cc

src/MissionManager/CorridorScanComplexItemTest.cc

src/MissionManager/MissionCommandList.h

src/MissionManager/MissionCommandTreeTest.cc

src/MissionManager/MissionCommandUIInfo.h

src/MissionManager/MissionController.cc

src/MissionManager/MissionController.h

src/MissionManager/MissionControllerManagerTest.cc

src/MissionManager/MissionControllerTest.cc

src/MissionManager/MissionItem.h

src/MissionManager/MissionItemTest.cc

src/MissionManager/MissionManagerTest.cc

src/MissionManager/MissionSettingsItem.cc

src/MissionManager/MissionSettingsTest.cc