libfeedback: Only cancel feedbacks if ever inited

If lfb_init() wasn't called before lfb_uninit() we'd otherwise raise a
critical which isn't nice for a library.

Signed-off-by: Guido Günther <agx@sigxcpu.org>

tests/test-lfb-main.c

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2025 The Phosh Developers
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ *
+ * Author: Guido Günther <agx@sigxcpu.org>
+ */
+
+#include "libfeedback.h"
+#include <gio/gio.h>
+
+/* unpaired uninit not raise any criticals */
+static void
+test_lfb_main_uninit (void)
+{
+  g_assert_false (lfb_is_initted ());
+  lfb_uninit ();
+  g_assert_false (lfb_is_initted ());
+}
+
+gint
+main (gint argc, gchar *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_autoptr(GTestDBus) bus = g_test_dbus_new (G_TEST_DBUS_NONE);
+  g_test_dbus_up (bus);
+
+  g_test_add_func ("/feedbackd/libfeedback/lfb-main/uninit", test_lfb_main_uninit);
+
+  return g_test_run();
+}