AV in pipeline demo

Hi,

I consistently get an access violation in the HL-III pipeline demo (This is the web spider demo). (http://www.omnithreadlibrary.com/webinars/code/HL-III.zip)

I'm not sure if this is due to a bug in OTL or perhaps in the code in the demo.

How to reproduce:
I make 1 simple change to the demo. In the method TfrmWebSpider.ExtractLinks:

```
for url in parser.Parsed.Hyperlinks do
//if not StartsText('http', url) then
begin
FURLCount.Increment;
FSpider.Input.TryAdd(url);
end;
```

I comment out the "if" statement. So now the demo will go for all links. If run this way the program will download a total of 90 links in a short time.

I press start, then after about 10 entries have been added I press "Stop". The program waits and then comes up with an AV.

I'm using DXE4, Win 7 x64