Only get spawn block if it's relevant, fixes #3934 (#3942)

Spigot-Server-Patches/0545-Fix-SPIGOT-5989.patch

@@ -10,7 +10,7 @@ This fixes that by checking if the modified spawn location is
 still at a respawn anchor.
 
 diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
-index 3c2f1f140c3991195bb8147bd65d9cd16a8fd3da..b8ec7941784885ace0c33fdf768ddcba284a12f9 100644
+index 9e438590113b2c7a318c812637c8aa14341df3e6..9382e8f79e8edec8885c629a36e230fbec50e1fb 100644
 --- a/src/main/java/net/minecraft/server/PlayerList.java
 +++ b/src/main/java/net/minecraft/server/PlayerList.java
 @@ -766,6 +766,7 @@ public abstract class PlayerList {
@@ -51,8 +51,8 @@ index 3c2f1f140c3991195bb8147bd65d9cd16a8fd3da..b8ec7941784885ace0c33fdf768ddcba
 -        if (flag2) {
 -            entityplayer1.playerConnection.sendPacket(new PacketPlayOutNamedSoundEffect(SoundEffects.BLOCK_RESPAWN_ANCHOR_DEPLETE, SoundCategory.BLOCKS, (double) blockposition.getX(), (double) blockposition.getY(), (double) blockposition.getZ(), 1.0F, 1.0F));
 +        // Paper start - Fix SPIGOT-5989
-+        IBlockData data = worldserver1.getType(blockposition);
 +        if (flag2 && !isLocAltered) {
++            IBlockData data = worldserver1.getType(blockposition);
 +            worldserver1.setTypeAndData(blockposition, data.set(BlockRespawnAnchor.a, data.get(BlockRespawnAnchor.a) - 1), 3);
 +            entityplayer1.playerConnection.sendPacket(new PacketPlayOutNamedSoundEffect(SoundEffects.BLOCK_RESPAWN_ANCHOR_DEPLETE, SoundCategory.BLOCKS, (double) location.getX(), (double) location.getY(), (double) location.getZ(), 1.0F, 1.0F));
 +        // Paper end