You need to be prepared for the fact that in many cases the interpreter will not show any error, even when an application crash or display a white screen. Simply put, when an error occurs in Thunkable X program or will not perform blocks, or will crash with serious problems.
Why is this happening? Because in web development and mobile development using the following concept - the application should be as user friendly. It should be understood in the sense that the user should not be aware of errors in it and the appearance of the majority of minor bugs simply suppressed and not displayed. The error is displayed only when the system crash. And in this case, an error message will display the system itself. In your example you have not done anything wrong in terms of Thunkable X, so it can work on.