UI: If Twitch account disconnected, retry login

If the user disconnects OBS from their Twitch account on their Twitch
settings panel, then try asking the user if they'd like to reconnect
before throwing an error.

UI/auth-twitch.cpp

@@ -102,8 +102,16 @@ try {
 		throw ErrorInfo("Failed to parse json", error);
 
 	error = json["error"].string_value();
-	if (!error.empty())
+	if (!error.empty()) {
+		if (error == "Unauthorized") {
+			if (RetryLogin()) {
+				return GetChannelInfo();
+			}
+			throw ErrorInfo(error,
+					json["message"].string_value());
+		}
 		throw ErrorInfo(error, json["error_description"].string_value());
+	}
 
 	name = json["name"].string_value();
 	key_ = json["stream_key"].string_value();