Please describe the problem:
When you save an image file as an ICO file when you index it, the file is saved
as all black.  Also, when saving as 4-bit ICO, the icon doesn't save properly as
some details are left out.

Steps to reproduce:
1.  Open the XCF sample file I attached.
2.  Index it (256 maximum colors with no dithering).
3.  Save it as an ICO in 4, 8, or 32-bit color mode.
4.  View the file by reopening it (the icon shown in the open recent dialog is
okay, but seeing the opened image file in GIMP or via Windows Explorer is where
it's all black.

Actual results:
The icon is saved as all black without any color at all.

Expected results:
The colors should be kept as is, unless there are more colors in the image than
the palette can store where extras are merged into existing ones or deleted
still leaving the image relatively in tact.

Does this happen every time?
As far as I can tell, yes.

Other information:
When saving into 4-bit mode without indexing it, the top 11 or so pixels are cut
off, but the icon appears fine otherwise.  This doesn't seem to apply to 8-bit
or 32-bit mode.