Return earlier, predict list's size for tab clearing

proxy/src/main/java/com/velocitypowered/proxy/tablist/VelocityTabList.java

@@ -89,15 +89,17 @@ public class VelocityTabList implements TabList {
    * MinecraftConnection#flush()}.
    */
   public void clearAll() {
-    List<PlayerListItem.Item> items = new ArrayList<>();
+    Collection<VelocityTabListEntry> listEntries = entries.values();
-    for (TabListEntry value : entries.values()) {
+    if (listEntries.isEmpty()) {
+      return;
+    }
+    List<PlayerListItem.Item> items = new ArrayList<>(listEntries.size());
+    for (TabListEntry value : listEntries) {
       items.add(PlayerListItem.Item.from(value));
     }
     entries.clear();
-    if (!items.isEmpty()) {
     connection.delayedWrite(new PlayerListItem(PlayerListItem.REMOVE_PLAYER, items));
   }
-  }
 
   @Override
   public Collection<TabListEntry> getEntries() {