Enabling dark mode feature and introduction

Hi everyone,
Thanks to the technician who taught me to develop dark mode, I’ve been adding dark mode in some of my pages in app inventor. Today I will introduce how to use and I also have some problems of not turning on the dark mode.
The method I used is the tinyDB, by adding the same tinyDB into the hidden part of the phone (though it is already hidden) to store the dark mode into your phone’s storage, here is the example (photo 1)

The problem I am facing right now is when I use my phone to test the app by not using the dark mode, I turned to the page which I have put the dark mode code into and the app said I had an error, I tried to fix but it still appears.
Here is the code that I’ve written.
If you read this message and have some ideas about the dark mode introduction or solve the problem, please leave the comment to share, thank you!

  1. The error probably comes from your empty sockets (see image) Just put an empty text block there if you want nothing, or better put a white colour block…

  1. You are not switching screens correctly (not related to your error)
Use different screens wisely

If you decided to use different screens, then you should switch them correctly, else you will run out of memory after a while...      
The recommended method of switching screens in App Inventor
(Thanks Taifun)
Also see demo: multiscreen.aia

The empty sockets were made intentionally to ask if anyone can tell me the solution, sorry for the unclear message.
I have tested the solutions that you gave me but there are also have some problems.

I have a text set in the black circle and they become white after adding a white block......