Voice Server Update endpoint is nullable (#1741)

docs/topics/Gateway.md

@@ -1195,13 +1195,16 @@ Sent when someone joins/leaves/moves voice channels. Inner payload is a [voice s
 
 Sent when a guild's voice server is updated. This is sent when initially connecting to voice, and when the current voice instance fails over to a new server.
 
+> warn
+> A null endpoint means that the voice server allocated has gone away and is trying to be reallocated. You should attempt to disconnect from the currently connected voice server, and not attempt to reconnect until a new voice server is allocated.
+
 ###### Voice Server Update Event Fields
 
 | Field    | Type      | Description                               |
 |----------|-----------|-------------------------------------------|
 | token    | string    | voice connection token                    |
 | guild_id | snowflake | the guild this voice server update is for |
-| endpoint | string    | the voice server host                     |
+| endpoint | ?string   | the voice server host                     |
 
 ###### Example Voice Server Update Payload