[PATCH v3 10/13] ui/dbus: Clean up dbus_update_gl_cb() error checking

[Markus Armbruster <armbru@redhat.com>]

From GLib "Rules for use of GError":

    A GError* must be initialized to NULL before passing its address
    to a function that can report errors.

dbus_update_gl_cb() seemingly violates this rule: it passes &err to
qemu_dbus_display1_listener_call_update_dmabuf_finish() and to
qemu_dbus_display1_listener_win32_d3d11_call_update_texture2d_finish()
without clearing it in between.  Harmless, because the first call is
guarded by #ifdef CONFIG_GBM, the second by #ifdef WIN32, and the two
are mutually exclusive.  I think.

Clean this up to be obviously correct.

Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 ui/dbus-listener.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/ui/dbus-listener.c b/ui/dbus-listener.c
index 42875b8eed..09d7a319b1 100644
--- a/ui/dbus-listener.c
+++ b/ui/dbus-listener.c
@@ -221,18 +221,21 @@ static void dbus_update_gl_cb(GObject *source_object,
 #ifdef CONFIG_GBM
     success = qemu_dbus_display1_listener_call_update_dmabuf_finish(
         ddl->proxy, res, &err);
+    if (!success) {
+        error_report("Failed to call update: %s", err->message);
+    }
 #endif
 
 #ifdef WIN32
     success = qemu_dbus_display1_listener_win32_d3d11_call_update_texture2d_finish(
         ddl->d3d11_proxy, res, &err);
-    d3d_texture2d_acquire0(ddl->d3d_texture, &error_warn);
-#endif
-
     if (!success) {
         error_report("Failed to call update: %s", err->message);
     }
 
+    d3d_texture2d_acquire0(ddl->d3d_texture, &error_warn);
+#endif
+
     graphic_hw_gl_block(ddl->dcl.con, false);
     g_object_unref(ddl);
 }
-- 
2.49.0