gpg: Fix segv importing certain keys.
* g10/key-check.c (key_check_all_keysigs): Initialize issuer.
- Fixes-commit: 404fa8211b6188a0abe83ef43a4b44d528c0b035
- Signed-off-by: Werner Koch <firstname.lastname@example.org>
See https://bugzilla.opensuse.org/show_bug.cgi?id=1176034 for the original bug report. I was not able to replicate the crash but the bad reads. The error is pretty obvious: The code expects that all fields are zeroed out.