Fix Key#getPrimaryUser on keys without valid UIDs

During tests of weird keys [0] it was found out that OpenPGP.js does not
handle keys without valid UIDs well.

There are two issues that this change corrects, first one is adding
filtering of user IDs in `getPrimaryUser` such as only users with self
certifications are considered. Without that change using
`getPrimaryUser` on a key without valid UIDs would throw an exception
(`Cannot read property 'verified' of undefined` [1]).

Second issue is correcting condition whether to throw if no UID was
found. Previous condition checked for `userId` variable, but this is
initialized by default and as such is almost always set. This causes
`key.getPrimaryUser()` (without condition) to throw `Could not find user
that matches that user ID`. The condition has been modified to match the
filter condition (checking if any property of `userId` has been
initialized).

[0]: https://gitlab.com/sequoia-pgp/weird-keys/tree/master/openpgpjs

[1]: 576ed08a54/openpgpjs/results/no-bound-uid.pgp.txt

src/key.js

@@ -494,15 +494,16 @@ Key.prototype.getPrimaryUser = async function(date=new Date(), userId={}) {
   const users = this.users.map(function(user, index) {
     const selfCertification = getLatestSignature(user.selfCertifications, date);
     return { index, user, selfCertification };
-  }).filter(({ user }) => {
-    return user.userId && (
+  }).filter(({ user, selfCertification }) => {
+    return user.userId && selfCertification && (
       (userId.name === undefined || user.userId.name === userId.name) &&
       (userId.email === undefined || user.userId.email === userId.email) &&
       (userId.comment === undefined || user.userId.comment === userId.comment)
     );
   });
   if (!users.length) {
-    if (userId) {
+    if (userId.name !== undefined || userId.email !== undefined ||
+        userId.comment !== undefined) {
       throw new Error('Could not find user that matches that user ID');
     }
     return null;

test/general/key.js

@@ -1303,6 +1303,25 @@ p92yZgB3r2+f6/GIe2+7
     expect(primUser.selfCertification).to.be.an.instanceof(openpgp.packet.Signature);
   });
 
+  it('getPrimaryUser() should return null if no UIDs are bound', async function() {
+    const keyWithoundBoundUid = `-----BEGIN PGP PRIVATE KEY BLOCK-----
+
+xVgEWxpFkRYJKwYBBAHaRw8BAQdAYjjZLkp4qG7KAqJeVQlxQT6uCPq6rylV02nC
+c6D/a8YAAP0YtS4UeLzeJGSgjGTlvSd3TWEsjxdGyzwfHCOejXMRbg2+zSFVbmJv
+dW5kIFVJRCA8dW5ib3VuZEBleGFtcGxlLm9yZz7HXQRbGkWREgorBgEEAZdVAQUB
+AQdAfxbFuoNlm5KfoqaWICETfMljzVTDAtiSM0TYSHzGAz8DAQoJAAD/cuu7bxUE
+goBAhIyVH+pmvWpuDJbfu1Vaj5KiQxsKxJgP/MJ+BBgWCgAwApsMBYJbGkWRBYkB
+3+IAFqEE30YL4fxJBMTm8ONLPOiTkVxEIS8JkDzok5FcRCEvAABb+gEAnQb/rMLO
+Vz/bMCJoAShgybW1r6kRWejybzIjFSLnx/YA/iLZeo5UNdlXRJco+15RbFiNSAbw
+VYGdb3eNlV8CfoEC
+=FYbP
+-----END PGP PRIVATE KEY BLOCK-----
+`;
+    const key = openpgp.key.readArmored(keyWithoundBoundUid).keys[0];
+    const primUser = await key.getPrimaryUser();
+    expect(primUser).to.be.null;
+  });
+
   it('Generated key is not unlocked by default', function() {
     const opt = {numBits: 512, userIds: 'test <a@b.com>', passphrase: '123'};
     if (openpgp.util.getWebCryptoAll()) { opt.numBits = 2048; } // webkit webcrypto accepts minimum 2048 bit keys