polkit: do not shadow dbus errors, avoid panic in case of errors

With the current code, when the dbus call fails with an error we will shadow it
with our own error. In the process of doing so, we try to access a map in
authResult that is uninitialized, accessing a key will cause a panic.

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

polkit/authority.go

@@ -49,7 +49,10 @@ func checkAuthorization(subject authSubject, actionId string, details map[string
 	err = authority.Call(
 		"org.freedesktop.PolicyKit1.Authority.CheckAuthorization", 0,
 		subject, actionId, details, flags, "").Store(&result)
-	if err != nil || !result.IsAuthorized {
+	if err != nil {
+		return false, err
+	}
+	if !result.IsAuthorized {
 		if result.IsChallenge {
 			err = ErrInteraction
 		} else if result.Details["polkit.dismissed"] != "" {