Do not run scripts in about:blank
Do not run scripts in about:blank

(Unless _specifically_ requested.)  Fixes #1298

the8472/greasemonkey,Martii/greasemonkey,Martii/greasemonkey,the8472/greasemonkey,Ventero/greasemonkey,HasClass0/greasemonkey,HasClass0/greasemonkey,Ventero/greasemonkey