Duplicate keywurl bug in 1.4b7

[mee]

In contrast to bug #5, I am able to create two keywurls(?) with the same keyword, even if they have different behaviors. When I go to the preferences pane, they are both visible in the list, but I can only get the detailed (url) view of the first one.

The reasonable behavior seems to be that if you try to create a new keywurl with the same keyword as an extant one, it should bark at you and throw you back to the keyword entry dialog or notify you that one exists and allow you to overwrite it.

Thanks for the great plugin.