What is the default value of the numeric entry box?

Hello Ahmed, 

Thanks for reaching out! 

One way to prevent states from triggering when nothing is entered in a numeric entry box is to associate a trigger with the 'when variable changes' event, similar to what is shown in this screenshot: 

This will make it so that an action will only occur if a valid number is entered in a numeric entry box. I've attached a sample project file to demonstrate this behavior. 

Let me know if you have any questions!