SPIGOT-4870: Server crashes while charging crossbow

nms-patches/ItemCrossbow.patch

@@ -18,7 +18,19 @@
      }
  
      @Override
-@@ -203,11 +207,27 @@
+@@ -88,6 +92,11 @@
+                 itemstack1 = new ItemStack(Items.ARROW);
+                 itemstack2 = itemstack1.cloneItemStack();
+             }
++            // CraftBukkit start - SPIGOT-4870, MC-150847
++            else if (itemstack1.isEmpty()) {
++                return;
++            }
++            // CraftBukkit end
+ 
+             a(entityliving, itemstack, itemstack1, k > 0, flag);
+         }
+@@ -203,11 +212,27 @@
                  vector3fa.a(quaternion);
                  ((IProjectile) object).shoot((double) vector3fa.a(), (double) vector3fa.b(), (double) vector3fa.c(), f1, f2);
              }