metadata: Prevent usage of NULL if GUdevDevice is not found

Code to determine tree name from device has been recently ported from
udev to gudev by commit c2d8564. Unfortunately, the gudev code floods
logs by the following messages if device is not found (it can happen
e.g. for tmpfs):
g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed

Udev code silently returned if NULL device was used, however, corresponding
gudev code prints the mentioned messages. Let's prevent usage of NULL
device in order to prevent those messages.

https://bugzilla.gnome.org/show_bug.cgi?id=795191

1 files changed, 8 insertions, 6 deletions

diff --git a/metadata/meta-daemon.c b/metadata/meta-daemon.c
index 444a4394..26edfcb3 100644
--- a/metadata/meta-daemon.c
+++ b/metadata/meta-daemon.c
@@ -319,13 +319,15 @@ handle_get_tree_from_device (GVfsMetadata *object,
     g_once_init_leave (&gudev_client, g_udev_client_new (NULL));
 
   device = g_udev_client_query_by_device_number (gudev_client, G_UDEV_DEVICE_TYPE_BLOCK, devnum);
+  if (device != NULL)
+    {
+      if (g_udev_device_has_property (device, "ID_FS_UUID_ENC"))
+        res = g_strconcat ("uuid-", g_udev_device_get_property (device, "ID_FS_UUID_ENC"), NULL);
+      else if (g_udev_device_has_property (device, "ID_FS_LABEL_ENC"))
+        res = g_strconcat ("label-", g_udev_device_get_property (device, "ID_FS_LABEL_ENC"), NULL);
 
-  if (g_udev_device_has_property (device, "ID_FS_UUID_ENC"))
-    res = g_strconcat ("uuid-", g_udev_device_get_property (device, "ID_FS_UUID_ENC"), NULL);
-  else if (g_udev_device_has_property (device, "ID_FS_LABEL_ENC"))
-    res = g_strconcat ("label-", g_udev_device_get_property (device, "ID_FS_LABEL_ENC"), NULL);
-
-  g_clear_object (&device);
+      g_clear_object (&device);
+    }
 #endif
 
   gvfs_metadata_complete_get_tree_from_device (object, invocation, res ? res : "");