Include fireworks in other-explosion flag.

Unfortunately, since fireworks neither have a "shooter" entity nor fire an EntityExplode,
the only way to mitigate damage is a complete on/off for any damage they cause.

Fortunately (probably), this should not interfere with elytra boosting, since the
acceleration is applied directly to the player upon use, not from the firework "explosion".

Fixes WORLDGUARD-3786.

worldguard-legacy/src/main/java/com/sk89q/worldguard/bukkit/listener/RegionFlagsListener.java

@@ -39,6 +39,7 @@
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.EventPriority;
 import org.bukkit.event.entity.EntityDamageEvent;
+import org.bukkit.event.entity.EntityDamageByEntityEvent;
 import org.bukkit.event.entity.EntityDamageEvent.DamageCause;
 
 import javax.annotation.Nullable;
@@ -106,17 +107,29 @@ public void onEntityDamage(EntityDamageEvent event) {
         if (entity instanceof Player && event.getCause() == DamageCause.FALL) {
             if (!query.testState(entity.getLocation(), (Player) entity, DefaultFlag.FALL_DAMAGE)) {
                 event.setCancelled(true);
+                return;
             }
         } else {
             try {
                 if (entity instanceof Player && event.getCause() == DamageCause.FLY_INTO_WALL) {
                     if (!query.testState(entity.getLocation(), (Player) entity, DefaultFlag.FALL_DAMAGE)) {
                         event.setCancelled(true);
+                        return;
                     }
                 }
             } catch (NoSuchFieldError ignored) {
             }
         }
+
+        if (event instanceof EntityDamageByEntityEvent) {
+            Entity damager = (((EntityDamageByEntityEvent) event)).getDamager();
+            if (damager != null && damager.getType() == EntityType.FIREWORK) {
+                if (!query.testState(entity.getLocation(), (RegionAssociable) null, DefaultFlag.OTHER_EXPLOSION)) {
+                    event.setCancelled(true);
+                    return;
+                }
+            }
+        }
     }
 
     /**