Description of problem:
When using the 'lighten only' blending mode on x86_64.

Version-Release number of selected component (if applicable):
2.2.2-3

How reproducible:
100%

Steps to Reproduce:
1. Open any image, or create a new one.
2. Create a new layer on top of it, entirely white.
3. Using the layers dialog, set the blending mode of the white layer to "Lighten
only".
  
Actual results:
The original layer shows through partially.

Expected results:
Entirely white image.