The spec says that CbColorTable field is present when Bpp is 1, 4, 8.
Actually, bpp == 2 is not supported by TS_ICON_INFO according to the
spec (though, DIB definitely supports 16-color images).
MS-RDPERP 2.2.1.2.3 Icon Info (TS_ICON_INFO)
CbColorTable (2 bytes):
This field is ONLY present if the bits per pixel (Bpp)
value is 1, 4, or 8.
Omitting 8-bit value breaks 256-color icons which are incorrectly
read with color and alpha data mixed up.
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