Merged in fix/453_zero_dt (pull request #426)

Throw exception when dt <= 0
close Issue #453

gtsam/navigation/ImuFactor.cpp

@@ -52,6 +52,11 @@ void PreintegratedImuMeasurements::resetIntegration() {
 //------------------------------------------------------------------------------
 void PreintegratedImuMeasurements::integrateMeasurement(
     const Vector3& measuredAcc, const Vector3& measuredOmega, double dt) {
+  if (dt <= 0) {
+    throw std::runtime_error(
+        "PreintegratedImuMeasurements::integrateMeasurement: dt <=0");
+  }
+
   // Update preintegrated measurements (also get Jacobian)
   Matrix9 A;  // overall Jacobian wrt preintegrated measurements (df/dx)
   Matrix93 B, C;