gen.go: fixed bug in version printing

Change-Id: I25e3d7407a037494774810cf0e50741229affae3
Reviewed-on: https://go-review.googlesource.com/24497
Reviewed-by: Nigel Tao <nigeltao@golang.org>
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
1 file changed