Check if firework item explosions tag is null (#626)

connector/src/main/java/org/geysermc/connector/network/translators/item/translators/nbt/FireworkTranslator.java

@@ -39,6 +39,7 @@ public class FireworkTranslator extends NbtItemStackTranslator {
         CompoundTag fireworks = itemTag.get("Fireworks");
 
         ListTag explosions = fireworks.get("Explosions");
+        if (explosions != null) {
             for (Tag effect : explosions.getValue()) {
                 CompoundTag effectData = (CompoundTag) effect;
 
@@ -84,6 +85,7 @@ public class FireworkTranslator extends NbtItemStackTranslator {
                 explosions.add(newEffectData);
             }
         }
+    }
 
     @Override
     public void translateToJava(CompoundTag itemTag, ItemEntry itemEntry) {