Improve damage handling of dead entities

nms-patches/EntityLiving.patch

@@ -492,6 +492,15 @@
          }
      }
  
+@@ -703,7 +903,7 @@
+             return false;
+         } else if (this.world.isClientSide) {
+             return false;
+-        } else if (this.getHealth() <= 0.0F) {
++        } else if (this.dead || this.killed || this.getHealth() <= 0.0F) { // CraftBukkit - Don't allow entities that got set to dead/killed elsewhere to get damaged and die
+             return false;
+         } else if (damagesource.p() && this.hasEffect(MobEffects.FIRE_RESISTANCE)) {
+             return false;
 @@ -958,6 +1191,12 @@
                      boolean flag = this.lastDamageByPlayerTime > 0;