[polari] telepathyClient: Fix incorrect usernameSupported setting

[Florian Müllner <fmuellner src gnome org>]

commit 570e141251ba4f8a25026f2e3b4590b936bd0826
Author: Алексей Шилин <rootlexx mail ru>
Date:   Sat Oct 26 18:50:26 2019 +0300

    telepathyClient: Fix incorrect usernameSupported setting
    
    g_match_info_fetch(), used by polari_util_match_identify_message()
    to retrieve username from identify message, returns an empty string
    if no username was provided. Hence comparing the result against null
    is incorrect.
    
    https://gitlab.gnome.org/GNOME/polari/merge_requests/136

 src/telepathyClient.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/telepathyClient.js b/src/telepathyClient.js
index 2358636..3adbf2a 100644
--- a/src/telepathyClient.js
+++ b/src/telepathyClient.js
@@ -636,7 +636,7 @@ class TelepathyClient extends Tp.BaseClient {
             botname: room.channel.target_contact.alias,
             command,
             username: username || room.channel.connection.self_contact.alias,
-            usernameSupported: username !== null,
+            usernameSupported: !!username,
             password,
         };
         this._pendingBotPasswords.set(accountPath, data);