js: Fix errorDetails of GPGME_Signature
js: Fix errorDetails of GPGME_Signature

* lang/js/src/Signature.js (GPGME_Signature.errorDetails):
Access properties from the summary object.

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme