^D in the average word length example causes weird behavior

[1-p]

In this example, https://github.com/edwinb/TypeDD-Samples/blob/master/Chapter2/AveMain.idr, entering ^D just cause an infinite stream of "Enter a string: The average word length is: nan". Is this expected or a bug?

I expect it to show "Enter a string: The average word length is: nan" just once.