clang-tidy modernize-use-nullptr

.clang-tidy

src/drivers/device/ringbuffer.cpp

src/drivers/device/vdev.cpp

src/drivers/device/vdev_posix.cpp

src/drivers/gps/gps.cpp

src/drivers/pwm_out_sim/pwm_out_sim.cpp

src/drivers/vmount/vmount.cpp

...es/attitude_estimator_ekf/attitude_estimator_ekf_main.cpp

...ples/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp

src/examples/fixedwing_control/main.cpp

..._att_control_multiplatform/mc_att_control_start_nuttx.cpp

..._pos_control_multiplatform/mc_pos_control_start_nuttx.cpp

src/lib/controllib/block/Block.cpp

src/lib/controllib/block/BlockParam.cpp

src/lib/launchdetection/LaunchDetector.cpp

src/lib/runway_takeoff/RunwayTakeoff.cpp

src/modules/commander/commander.cpp

src/modules/commander/mag_calibration.cpp

src/modules/commander/state_machine_helper.cpp

src/modules/controllib_test/controllib_test_main.cpp