Using 1.3.8a and latest SbA and have a small error.

Admin > catalog > products with attributes stock
Click > 'Add quantity for product variant'
Size (only attribute) - 'All'
Quantity - Any number

Hit 'Submit'

I then get this error:
att: 41|42|43|44|45|46

Warning: Cannot modify header information - headers already sent by (output started at /home/path/to/products_with_attributes_stock.php:193) in /home/path/to/admin/includes/functions/general.php on line 21

Line 193 - echo "att: $attributes<bR>\n";
Line 21 - header('Location: ' . $url);

I thought maybe the R in bR was wrong (line break?) but changing it made no difference.

Thing is, although this error occurs hitting back button and accessing 'Admin > catalog > products with attributes stock' again shows the options updated correctly.

Other than that everything works perfect.

Any suggestions to get rid of the error before I show to the client?