Fix lookup of ECC OIDs by name.
* src/keyinfo.c (get_ecc_curve_oid): Fix obviously never tested table lookup.
This led to a crash see
https://lists.gnupg.org/pipermail/gnupg-devel/2015-October/030445.html
The fix is obvious but I do not have test data for this.
- Signed-off-by: Werner Koch <wk@gnupg.org>