Fragment scopes get cancelled when the fragment goes away, but we don't
actually want to cancel an in-flight transition in that case. Also,
before when the fragment would cancel, there'd be an exception, and the
exception handler would call Fragment::getString, which in turn called
requireContext, which caused an exception. Work around this by using the
`activity ?: Application.get()` idiom to always have a context for
strings and toasts.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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