[tx] cffread wrong glyph widths for CFF2 VF instance

[blueshade7]

cffread appears to output glyph widths for an instance of a CFF2 variable font by blending HVAR deltas using scalar values calculated from VariationStore in the CFF2 table incorrectly.
The attached font is a copy of AdobeVFPrototype.otf modified to contain regions in a shuffled order so it becomes different from that in CFF2. The font should behave functionally the same as the original.
AdobeVFPrototype_shuffled.otf.zip (replaced a bad copy)

% tx -3 -g W -U 900,0 AdobeVFPrototype_shuffled.otf

## glyph[tag] {name,encoding,path}
glyph[56] {W,U+0057,
  966 width

The glyph width 966 is incorrect, should match the width from the original:

% tx -3 -g W -U 900,0 AdobeVFPrototype.otf

## glyph[tag] {name,encoding,path}
glyph[56] {W,U+0057,
  989 width