Fix a bug where removing wouldn't update arrow

diff --git a/TomTomLite.lua b/TomTomLite.lua
index 705ae1a..8b088ac 100644
--- a/TomTomLite.lua
+++ b/TomTomLite.lua
@@ -59,6 +59,7 @@ function addon:Initialize()
     self.arrow:Hide()

     self:RegisterMessage("TOMTOMLITE_WAYPOINT_ADDED")
+    self:RegisterMessage("TOMTOMLITE_WAYPOINT_DELETED")
     self:RegisterMessage("TOMTOMLITE_WAYPOINTS_CHANGED")

     -- Events for world map overlays