public static <T, R> Function<T, R> ifNull(Function<T, R> f) {
		return f == null ? function() : f;
	}
Returns the given function object if it is not {@code null}.  Otherwise, a
{@link #function()} is returned.  This is useful to avoid using {@code null}.

@param <T> the input type
@param <R> the result type
@param f the function to check for {@code null}
@return a non-null function
Ghidra/Framework/Utility/src/main/java/utility/function/Dummy.java