[skip ci] const ref variable

src/processor/processor_imu.cpp

@@ -282,7 +282,7 @@ void ProcessorImu::bootstrap()
 
                 // compute local g and transformation to global g
                 double      dt         = t_current - first_capture->getTimeStamp();  //
-                Vector3d    dv         = delta_int.segment(7, 3);                    //
+                const auto& dv         = delta_int.segment(7, 3);                    //
                 Vector3d    g_l        = -((q_l_r * q_r_s) * dv / dt);               // See eq. (20)
                 const auto& g_w        = gravity();                                  //
                 const auto& p_w_l      = Vector3d::Zero();                       // will pivot around the local origin