Do you accept a hacky approach, where we color the empty labels white?

dend %>% 
  set("leaves_pch", 19) %>% 
  set("leaves_cex", 2) %>% 
  set("leaves_col", leafcols) %>% 
  set("labels_col", ifelse(new_labels == "", "white", "black")) %>% 
  circlize_dendrogram(dend_track_height = 0.8)