Set cmd_dt to zero when detecting negative value

Instead of setting curr_cmd to zero, the correct approach is to set cmd_dt to zero and this will then keep the current control, without any abrupt change

Co-authored-by: Matt Reynolds <[email protected]>

ackermann_steering_controller/src/ackermann_steering_controller.cpp

@@ -321,12 +321,11 @@ namespace ackermann_steering_controller{
     }
 
     // Limit velocities and accelerations:
-    const double cmd_dt = (period.toSec() > 0) ? period.toSec() : 0.0;
-    if(cmd_dt < 0)
+    double cmd_dt(period.toSec());
+    if (cmd_dt < 0.0)
     {
       ROS_ERROR("Invalid time interval, delta time cannot be negative");
-      curr_cmd.lin = 0.0;
-      curr_cmd.ang = 0.0;
+      cmd_dt = 0.0;
     }
 
     limiter_lin_.limit(curr_cmd.lin, last0_cmd_.lin, last1_cmd_.lin, cmd_dt);