fix: (verify,decrypt) using isSigned to validate instead of SignedBy (#42)

Author: jerson

openpgp/decrypt.go

@@ -68,7 +68,7 @@ func (o *FastOpenPGP) decrypt(reader io.Reader, privateKey, passphrase string, s
 			return nil, fmt.Errorf("signature error: %w", md.SignatureError)
 		}
 
-		if md.SignedBy == nil {
+		if !md.IsSigned {
 			return nil, errors.New("message is not signed")
 		}
 

openpgp/verify.go

@@ -86,7 +86,7 @@ func (o *FastOpenPGP) verifyDataBytes(signedData io.Reader, publicKey string, sh
 		return false, fmt.Errorf("invalid read message: %w", err)
 	}
 
-	if md.SignedBy == nil {
+	if !md.IsSigned {
 		return false, errors.New("message was not signed")
 	}