hub: send an empty outfit as a list

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/hub/hub.go

@@ -273,7 +273,7 @@ func (c *Client) connect(ctx context.Context) error {
 	sentID, sentOutfit := int64(-1), ""
 	for {
 		c.mu.Lock()
-		id, outfit := c.imvuID, append([]Item(nil), c.outfit...)
+		id, outfit := c.imvuID, append([]Item{}, c.outfit...) // a list, never null
 		c.mu.Unlock()
 		if id != sentID && id != 0 {
 			if err := send(map[string]any{"type": "session", "imvu_id": id}); err != nil {