negative pattern doesn't match empty string in globbing?

[Han Pingtian <hanpt@xxxxxxxxxxxxxxxxxx>]

Hello,

I just notice that negative pattern like this doesn't work:

    localhost% setopt extendedglob
    localhost% print /usr/**/bin/zsh
    /usr/bin/zsh /usr/local/bin/zsh
    localhost% print /usr/^local/bin/zsh
    zsh: no matches found: /usr/^local/bin/zsh
    localhost% ls /usr//bin/zsh
    /usr//bin/zsh
    localhost% 

I think if "^local" can match with empty string, then this should work.
But looks like it doesn't.