This amends commit a0a990863fa54b52db5e97716b130f69de47fa52.
We bailed out of writing the filter file if opening the file for writing
was successful. The condition must be flipped.
Change-Id: I24331c5374a25c5a1126c6f7f71d41d840e0e532
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>