Re-apply naughty: Fix builds without dbus (d5088c5)

This got lost in 355f106 (naughty: Split up into core and dbus).

lib/naughty/dbus.lua.in

@@ -47,18 +47,22 @@ dbus.config.mapping = {
 }
 
 local function sendActionInvoked(notificationId, action)
+    if capi.dbus then
         capi.dbus.emit_signal("session", "/org/freedesktop/Notifications",
         "org.freedesktop.Notifications", "ActionInvoked",
         "i", notificationId,
         "s", action)
     end
+end
 
 local function sendNotificationClosed(notificationId, reason)
+    if capi.dbus then
         capi.dbus.emit_signal("session", "/org/freedesktop/Notifications",
         "org.freedesktop.Notifications", "NotificationClosed",
         "i", notificationId,
         "i", reason)
     end
+end
 
 local function convert_icon(w, h, rowstride, channels, data)
     -- Do the arguments look sane? (e.g. we have enough data)