Crashes app in iOS 12.2 due to using an "app"-type variable

To reproduce such an error again fails, but it was.

In the project, I created 4 variables of type “app '. After that, I create a new variable of type” app "with the name “oldIndex” and see how all variables “app msg” in the project change their name to “app oldIndex”. It turns out that I create a new variable, but at the same time the name of already existing variables is changed, whose name has nothing to do with the dialed one.

After that, I set the names back to the variables “app msg”, and I use the new variable (this variable is initialized with an empty side of the text block) in the timer and crash occurs right away.