abb0c49870
When a shape key is made the new basis key, also update the "Relative To" setting on the old & new basis keys. Both are made relative to the new basis shape key. Without this, the old basis key would still be relative to itself, which effectively disables it. By making it relative to the new basis key, you can increase its blend value to invert the effect of the new basis key. Pull Request: https://projects.blender.org/blender/blender/pulls/143466