Paper/nms-patches/ItemCrossbow.patch

--- a/net/minecraft/server/ItemCrossbow.java
+++ b/net/minecraft/server/ItemCrossbow.java
@@ -75,6 +75,11 @@
                 itemstack1 = new ItemStack(Items.ARROW);
                 itemstack2 = itemstack1.cloneItemStack();
             }
+            // CraftBukkit start - SPIGOT-4870, MC-150847
+            else if (itemstack1.isEmpty()) {
+                return false;
+            }
+            // CraftBukkit end
 
             if (!a(entityliving, itemstack, itemstack1, k > 0, flag)) {
                 return false;
@@ -198,11 +203,27 @@
                 vector3fa.a(quaternion);
                 ((IProjectile) object).shoot((double) vector3fa.a(), (double) vector3fa.b(), (double) vector3fa.c(), f1, f2);
             }
+            // CraftBukkit start
+            org.bukkit.event.entity.EntityShootBowEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callEntityShootBowEvent(entityliving, itemstack, itemstack1, (Entity) object, entityliving.getRaisedHand(), f, true);
+            if (event.isCancelled()) {
+                event.getProjectile().remove();
+                return;
+            }
+            // CraftBukkit end
 
             itemstack.damage(flag1 ? 3 : 1, entityliving, (entityliving1) -> {
                 entityliving1.broadcastItemBreak(enumhand);
             });
-            world.addEntity((Entity) object);
+            // CraftBukkit start
+            if (event.getProjectile() == ((Entity) object).getBukkitEntity()) {
+                if (!world.addEntity((Entity) object)) {
+                    if (entityliving instanceof EntityPlayer) {
+                        ((EntityPlayer) entityliving).getBukkitEntity().updateInventory();
+                    }
+                    return;
+                }
+            }
+            // CraftBukkit end
             world.playSound((EntityHuman) null, entityliving.locX(), entityliving.locY(), entityliving.locZ(), SoundEffects.ITEM_CROSSBOW_SHOOT, SoundCategory.PLAYERS, 1.0F, f);
         }
     }