Comment 8 for bug 926918

The attached patch as well as the commit 3069a7eaa5d83e7f41616347ba244c0dc0d944ae fix the bug. The commit 3069a7ea seems to be sufficient, what also explains why it even worked with mesa master before you commited 27e77cb902b4f7f5e127dcd78951e3167f13d59c. Thanks a lot :)