Kotlin Bootcamp issue: Lesson 2, Task 4, Step 2.2, error while running

[michaelarie96]

Describe the problem
When running, the kotlin REPL output is:

error: type mismatch: inferred type is Int? but Int was expected
fishFoodTreats = fishFoodTreats?.dec()

In which step of the codelab can this issue be found?
Task 4, Step 2.2

Steps to reproduce?
Run the code in kotlin REPL

Versions
2024.3

Additional information

codelab: kotlin-bootcamp