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Invoked when the application powering view fails with an uncaught exception. This function should display an error UI.
Typical implementations call TreehouseView.reset and display an error placeholder. Development builds may show more diagnostic information than production builds.
When a Treehouse app fails, its current Zipline instance is canceled so no further code will execute. A new Zipline will start when new code available.
This condition is not permanent! If new code is loaded after an error, onCodeLoaded will be called.