QueryString: Personalized content always shows, even if key has blank value

Description

Step to reproduce

1. Create a visitor group VG1 with criterion = Query String, Key = abc, Condition = Has Value, Value =< blank>.
2. Add VG1 to content1 of Page1.
3. View Page1 in view mode,
4. Ensure that the user does not have "abc" in the url.

Expected: content 1 does not appear.
Actual: content1 appears in Page1