Fixed possible ConcurrentModificationException when iterating across TabList entries (#1204)

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

@@ -38,7 +38,6 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.UUID;
-import java.util.stream.Collectors;
 import net.kyori.adventure.text.Component;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -62,7 +61,7 @@ public class VelocityTabList implements InternalTabList {
   public VelocityTabList(ConnectedPlayer player) {
     this.player = player;
     this.connection = player.getConnection();
-    this.entries = Maps.newHashMap();
+    this.entries = Maps.newConcurrentMap();
   }
 
   @Override
@@ -101,12 +100,11 @@ public class VelocityTabList implements InternalTabList {
     Preconditions.checkNotNull(entry.getProfile(), "Profile cannot be null");
     Preconditions.checkNotNull(entry.getProfile().getId(), "Profile ID cannot be null");
 
-    TabListEntry previousEntry = this.entries.put(entry.getProfile().getId(), entry);
+    this.entries.compute(entry.getProfile().getId(), (uuid, previousEntry) -> {
-
       if (previousEntry != null) {
         // we should merge entries here
         if (previousEntry.equals(entry)) {
-        return; // nothing else to do, this entry is perfect
+          return previousEntry; // nothing else to do, this entry is perfect
         }
         if (!Objects.equals(previousEntry.getDisplayNameComponent().orElse(null),
                 entry.getDisplayNameComponent().orElse(null))) {
@@ -165,6 +163,9 @@ public class VelocityTabList implements InternalTabList {
         playerInfoEntry.setLatency(entry.getLatency());
         playerInfoEntry.setListed(entry.isListed());
       }
+      return entry;
+    });
+
     this.connection.write(new UpsertPlayerInfoPacket(actions, List.of(playerInfoEntry)));
   }
 
@@ -186,7 +187,7 @@ public class VelocityTabList implements InternalTabList {
 
   @Override
   public Collection<TabListEntry> getEntries() {
-    return this.entries.values().stream().map(e -> (TabListEntry) e).collect(Collectors.toList());
+    return List.copyOf(this.entries.values());
   }
 
   @Override