[m-rev.] diff: fix unreachable return statements

[Julien Fischer]

On Fri, 1 Sep 2017, Zoltan Somogyi wrote:

> This fixes a bootcheck failure in Java grades,

Thanks for fixing that.

> but the Java grade still does not bootstrap. The problem is shown by
> the following messages, which implicate Julien's recent changes.

I'll take a look at that one.

Julien.