Use correct packet data for toggling flying. Fixes BUKKIT-4989

src/main/java/net/minecraft/server/PlayerConnection.java

@@ -1584,12 +1584,12 @@ public class PlayerConnection implements PacketPlayInListener {
     }
 
     public void a(PacketPlayInAbilities packetplayinabilities) {
-        // CraftBukkit start
-        if (this.player.abilities.canFly && this.player.abilities.isFlying != packetplayinabilities.f()) {
+        // CraftBukkit start - d() should be isFlying()
+        if (this.player.abilities.canFly && this.player.abilities.isFlying != packetplayinabilities.d()) {
             PlayerToggleFlightEvent event = new PlayerToggleFlightEvent(this.server.getPlayer(this.player), packetplayinabilities.f());
             this.server.getPluginManager().callEvent(event);
             if (!event.isCancelled()) {
-                this.player.abilities.isFlying = packetplayinabilities.f(); // Actually set the player's flying status
+                this.player.abilities.isFlying = packetplayinabilities.d(); // Actually set the player's flying status
             }
             else {
                 this.player.updateAbilities(); // Tell the player their ability was reverted