Fix: Silence warning of function having no return value

Some compilers complain that codepaths which assert have
no return value. This is valid since assertions could
be compiled-out, resulting in an undefined return value.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>