From The Apple Wiki
Original author(s)Apple Inc.
Developer(s)Apple Inc.
Stable release
Operating systemiOS
SizeN/A MB
Available inEnglish
LicenseClosed source

Null, NullBars, NullCanvas, NullPlus, NullSwift, NullPlusSwift, NullTimerTest, and NullWebContent are apps designed to ensure iOS is able to open and run apps written in various lanugages, such as Swift, WebKit, SwiftUI, and the like. They all open to blank white or black screens.