Error [libxml2-65]: ""

attributes construct error


The error is thrown because my URL is formed with an empty GET variable.
Like this:

This is done server-side because VAR1 can be empty or contain data.
Because VAR1 is empty in the link (this time) i get an error validating the link, the M in &

Is this an error in the validator?
Or is it not allowed to form URL's with GET variables who have empty data.

Thanks for your response.