You can fix it by pressing the RIGHT button on the mouse, the clicky thing, on the block thingy then press learn more and then it will send you to your download history and you can either say keep or discard the file... hope this helps!
Thanks for the help, I will be using the following now:
ArrayList<EntityPlayerMP> allp = new ArrayList<EntityPlayerMP>();
ListIterator itl;
for(int i = 0; i<MinecraftServer.getServer().worldServers.length; i++) {
itl = MinecraftServer.getServer().worldServers[i].playerEntities.listIterator();
while(itl.hasNext()) allp.add((EntityPlayerMP)itl.next());
}