Please describe the problem:
Scaling an image that contains layers with alpha channels doesn't work properly.  The alpha channel is preserved, but the R, G and B channels are cleared, i.e. set to black/zero.

This happens with PNG, JPG and XCF files and attempting to work around it via layers masks produces the same results.

Steps to reproduce:
1. Load or Make a new image.
2. Insure that at least one layer has an alpha channel.
3. Scale the image with Lanczos scaling (bigger or smaller).


Actual results:
Those layers that had alpha channels have the RGB channels set to black loosing all color information.

Expected results:
It'd be nice if the color information was preserved, :-).

Does this happen every time?
Yep

Other information:
This bug showed up in either 2.3.8 or shortly after it I believe.  I first noticed the problem in a post 2.3.8 CVS build (early to mid-May).  I didn't use 2.3.8 very much so I'm unsure if the bug was in 2.3.8.