Update deprecated email extraction in p_gpg_decrypt

Fixes arch build.

Since gpgme v2 release, https://github.com/gpg/gpgme/blob/master/NEWS, the gpgme_key_get_string_attr as well as GPGME_ATTR_EMAIL are REMOVED.

Fixes #2
Closes #2

src/pgp/gpg.c

@@ -656,11 +656,15 @@ p_gpg_decrypt(const char* const cipher)
             error = gpgme_get_key(ctx, recipient->keyid, &key, 1);
 
             if (!error && key) {
-                const char* addr = gpgme_key_get_string_attr(key, GPGME_ATTR_EMAIL, NULL, 0);
-                if (addr) {
-                    g_string_append(recipients_str, addr);
+                for (gpgme_user_id_t uid = key->uids; uid != NULL; uid = uid->next) {
+                    if (uid->email) {
+                        g_string_append(recipients_str, uid->email);
+                        break;
+                    }
                 }
                 gpgme_key_unref(key);
+            } else if (error) {
+                log_warning("GPGME error: %s", gpgme_strerror(error));
             }
 
             if (recipient->next) {