Rare crash: PreintegratedCombinedMeasurements::integrateMeasurement: dt <=0

[nashj]

I have run into this crash only a couple of times in several weeks of testing. It occurs if the timestamps between IMU messages are equal or if the former occurs after the latter. This indicates there may be a logic or race condition bug.

terminate called after throwing an instance of 'std::runtime_error'
  what():  PreintegratedCombinedMeasurements::integrateMeasurement: dt <=0
[serpent-7] process has died [pid 206604, exit code -6, cmd /home/william/catkin_ws/devel/lib/serpent/serpent_node serpent/input/imu:=/vectornav/IMU serpent/input/pointcloud:=/os_cloud_node/points serpent/input/stereo/left/image:=/eels1/front/left/image_rect serpent/input/stereo/right/image:=/eels1/front/right/image_rect serpent/input/stereo/left/camera_info:=/eels1/front/left/camera_info serpent/input/stereo/right/camera_info:=/eels1/front/right/camera_info serpent/input/barometer:=/altimeter_sensor/pressure __name:=serpent __log:=/home/william/.ros/log/f77470b8-b54d-11ed-b490-b5497b8a88f1/serpent-7.log].
log file: /home/william/.ros/log/f77470b8-b54d-11ed-b490-b5497b8a88f1/serpent-7*.log