Fixed some bugs that lead to a crash/bugs, when deleting objects

demos/optical_bench/src/hmd_navigation_behavior.cpp

demos/optical_bench/src/lens.cpp

demos/optical_bench/src/lens.hpp

demos/optical_bench/src/object_manager.cpp

demos/optical_bench/src/object_manager.hpp

demos/optical_bench/src/object_support_rod.cpp

demos/optical_bench/src/object_support_rod.hpp

demos/optical_bench/src/selection_system.cpp

demos/optical_bench/src/selection_system.hpp

demos/optical_bench/src/selector.hpp

demos/optical_bench/src/test_pattern_frame.cpp

demos/optical_bench/src/test_pattern_frame.hpp