Fix crashes in OpenPoseEstimation when onDisconnectImageProcessor is called

This fixes OpenPoseEstimation crashing whenever onDisconnectImageprocessor was called (for example when the ImageProvider was restarted).

Rationale

The problem was, that the member variable OpenPoseEstimation::calibration was deleted, and afterwards OpenPoseEstimation::stereoCalibration (instance of IVT StereoCalibration), resulting in a double-free or corruption. Double free in this case, since the destructor of StereoCalibration deletes the instance as well, as can be seen here. OpenPoseEstimation::calibration is initialised here from OpenPoseEstimation::stereoCalibration::GetLeftCalibration().