That thread may be useful to you. It seems like since the DS is printing a NullPointerException that something in your code is being referenced before initialization, specifically, during the period that the robot code is trying to start.
Mitch Stokes, it crashes a few seconds after hitting ‘enable’ in the Driver Station. Here’s the process: I deploy the error-free code; the driver station looks good to go; then I hit enable; I can’t drive the robot at all; then like 2 seconds later, it crashes and puts it back to disabled.
This sounds like a null pointer being called in either TeleopInit or TeleopPeriodic since the error comes when you enable in the teleoperated mode. Check all of your calls in those two methods to ensure they’re not referencing variables/objects that don’t exist.
That would be the problem (provided there’s not any other classes that modify speed). However, it is worth noting that the null pointer he/she is seeing isn’t from using an empty string (""), it’s from using a string with no value. That isn’t to say that using an empty string on the SmartDashboard wouldn’t throw a NullPointer or other exception, just that this specific null pointer is thrown by trying to access the value of a non-initialized field.