I don't expect that anyone will have time to comb through this program, but essentially what happens is that when you play and then use the game's save feature, it writes game data to the records. One of the columns is completedStars which is a list like [12, 35, 123]. When the game is loaded, the code attempts to read the table to get back to the game state. The list of completed star numbers comes back as a list like this [null, null, null]. I can look in the table and verify that in the table, the list does contain numbers. They turn into nulls when read from the table.
I wasn't able to understand why in the time I have looked at it, but I do know that reference types can act in unexpected ways. At least for novice programmers like myself!