Address some more `-Wunreachable-code` warnings.

Fixes #384.

Change-Id: I6b9e6e84017f78338ea0f916932a1af0c2668fa6
Reviewed-on: https://code-review.googlesource.com/c/re2/+/60371
Reviewed-by: Perry Lorier <perryl@google.com>
Reviewed-by: Paul Wankadia <junyer@google.com>
6 files changed