added assertions in getCalibration()

src/processor/processor_imu.cpp

@@ -87,6 +87,8 @@ FeatureBasePtr ProcessorImu::emplaceFeature(CaptureMotionPtr _capture_motion)
 
 VectorXd ProcessorImu::getCalibration (const CaptureBasePtr _capture) const
 {
+    assert(_capture && "called with a null capture");
+    assert(_capture->getSensorIntrinsic() && "null sensor intrinsics state block");
     return _capture->getSensorIntrinsic()->getState();
 }