Fix an ERROR caused by a list IndexError.

EXPERIMENTAL com.google.fonts/check/varfont/instances_in_order
On the Google Fonts profile

(issue #4626)

CHANGELOG.md

@@ -9,6 +9,13 @@ A more detailed list of changes is available in the corresponding milestones for
  - v0.12.0a3 (2024-Mar-13)
  - v0.12.0a4 (2024-Mar-15)
  - v0.12.0a5 (2024-Apr-02)
+ - v0.12.0a6 (2024-Apr-04)
+
+
+## 0.12.0a6 (2024-Apr-04)
+### Changes to existing checks
+#### On the Google Fonts profile
+ - **EXPERIMENTAL [com.google.fonts/check/varfont/instances_in_order]:** Fix an ERROR caused by a list IndexError (issue #4626)
 
 
 ## 0.12.0a5 (2024-Apr-02)

Lib/fontbakery/checks/googlefonts/varfont.py

@@ -653,7 +653,7 @@ def com_google_fonts_check_varfont_instances_in_order(ttFont, config):
  # Partition into sub-lists based on the other axes values.
  # e.g. "Thin Regular", "Bold Regular", "Thin Condensed", "Bold Condensed"
  # becomes [ ["Thin Regular", "Bold Regular"], ["Thin Condensed", "Bold Condensed"] ]
- sublists = []
+ sublists = [[]]
  last_non_wght = {}
  for coord in coords:
  non_wght = {k: v for k, v in coord.items() if k != "wght"}