gpg: Fix packet length checking in symkeyenc parser.
* g10/parse-packet.c (parse_symkeyenc): Move error printing to the end. Add additional check to cope for the 0je extra bytes needed for AEAD.
- Fixes-commit: 9aab9167bca38323973e853845ca95ae8e9b6871
- GnuPG-bug-id: T3780