Fix potential for NPE if receivers is null and the world was empty

Spigot-API-Patches/Expand-World.spawnParticle-API-and-add-Builder.patch

@@ -10,7 +10,7 @@ This adds a new Builder API which is much friendlier to use.
 
 diff --git a/src/main/java/com/destroystokyo/paper/ParticleBuilder.java b/src/main/java/com/destroystokyo/paper/ParticleBuilder.java
 new file mode 100644
-index 00000000..bf4edd07
+index 00000000..2bccc409
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/ParticleBuilder.java
 @@ -0,0 +0,0 @@
@@ -96,11 +96,13 @@ index 00000000..bf4edd07
 +     * @return If this particle is going to be sent to someone
 +     */
 +    public boolean hasReceivers() {
-+        return (receivers == null && !location.getWorld().getPlayers().isEmpty()) || !receivers.isEmpty();
++        return (receivers == null && !location.getWorld().getPlayers().isEmpty()) || (receivers != null && !receivers.isEmpty());
 +    }
 +
 +    /**
-+     * Sends this particle to all players in the world
++     * Sends this particle to all players in the world. This is rather silly and you should likely not be doing this.
++     *
++     * Just be a logical person and use receivers by radius or collection.
 +     */
 +    public ParticleBuilder allPlayers() {
 +       this.receivers = null;