bad blogmarks url validation

I`ve noticed that validation of blogmarks urls is incorrect.
In a few words:
When we posting blogmarks their urls are validating for dublication, but this feature wont`s work.
If i have a weblink with some url, and my users trying to post blogmark with the same url - it will be post! Really! They`ll get an attention page with words "A weblink nid using that link already exists" BUT blogmark will be posted!

p.s.
I tried to change an error request in weblink_validate function from form_set_error('weblink'... to print theme('page'...(like it done in function weblink_blogmark())
After that blogmarks stoped dublicating but if i have dublicating urls in my weblink-DB (this was only "empty" urls which i had have to do sometimes) and my lovely page node/add/weblink became consists of one Error Attention "A weblink nid using that link already exists":)))