Null reference exception?

I have a scenario in which when an object passes through colliders acting as triggers, a timer pops up on the screen then leaves the screen using an exit script. It works fine for the first trigger, but when the object reaches the second trigger everything goes whacko. The timer continues to flash onto the screen even though it should be inactive. I get a repeated error: “null reference exception, Object Reference not set to instance of an object in TimerUpdate()” for this line of my timer script (C#):

text.text = “Potential Eclipse:” + Mathf.Round(timeLeft);

(the timer is an eclipse countdown). I’m new to Unity, what does this mean and how can I fix it?

Your text reference is probably a null, do you destroy your text element?