Fix up NPE's in EntityMinecart/CraftVehicle and removed a little un-needed code in EntityArrow

src/main/java/net/minecraft/server/EntityArrow.java

@@ -178,9 +178,7 @@ public class EntityArrow extends Entity {
                     // or leave as DamageCause.ENTITY_ATTACK
                     org.bukkit.entity.Entity shooter = null;
                     if ((EntityLiving)b != null) {
-                        shooter = new org.bukkit.craftbukkit.entity.CraftLivingEntity(server, b);
-                    } else if ((Entity)b != null) {
-                        shooter = (org.bukkit.entity.Entity) b.getBukkitEntity();
+                        shooter = b.getBukkitEntity();
                     }
                     EntityDamageByProjectileEvent edbpe = new EntityDamageByProjectileEvent(shooter, entity.getBukkitEntity(), this.getBukkitEntity(), EntityDamageEvent.DamageCause.ENTITY_ATTACK, 4);
 

src/main/java/net/minecraft/server/EntityMinecart.java

@@ -183,7 +183,11 @@ public class EntityMinecart extends Entity implements IInventory, CraftMappable
 
     public boolean a(Entity entity, int i) {
         // CraftBukkit start
-        VehicleDamageEvent event = new VehicleDamageEvent(Type.VEHICLE_DAMAGE, (Vehicle) this.getBukkitEntity(), entity.getBukkitEntity(), i);
+        org.bukkit.entity.Entity passenger = null;
+        if ((EntityLiving)entity != null) {
+            passenger = entity.getBukkitEntity();
+        }
+        VehicleDamageEvent event = new VehicleDamageEvent(Type.VEHICLE_DAMAGE, (Vehicle) this.getBukkitEntity(), passenger, i);
         ((WorldServer)l).getServer().getPluginManager().callEvent(event);
 
         if (event.isCancelled()) {

src/main/java/org/bukkit/craftbukkit/entity/CraftVehicle.java

@@ -16,7 +16,7 @@ public abstract class CraftVehicle extends CraftEntity implements Vehicle {
     }
 
     public Entity getPassenger() {
-        return (getHandle().j.getBukkitEntity());
+        return isEmpty()?null:(getHandle().j.getBukkitEntity());
     }
     
     public boolean setPassenger(Entity passenger) {