Fix crash involving fireballs

nms-patches/IProjectile.patch

@@ -5,7 +5,7 @@
  import javax.annotation.Nullable;
  
 +// CraftBukkit start
-+import org.bukkit.entity.LivingEntity;
++import org.bukkit.projectiles.ProjectileSource;
 +// CraftBukkit end
 +
  public abstract class IProjectile extends Entity {
@@ -15,7 +15,7 @@
              this.shooter = entity.getUniqueID();
              this.c = entity.getId();
          }
-+        this.projectileSource = entity == null ? null : (LivingEntity) entity.getBukkitEntity(); // CraftBukkit
++        this.projectileSource = (entity instanceof ProjectileSource) ? (ProjectileSource) entity.getBukkitEntity() : null; // CraftBukkit
  
      }