e7b024a691
Since 3b5df8a7ea, we are displaying a "canvas picker" in the 3DView
header. In weightpaint mode, this gives us the active vertexgroup to
paint on, however the header wasnt updating when changing the
vertexgroup elsewhere (e.g. from the Properties Editor).
Part of #112186.
Pull Request: https://projects.blender.org/blender/blender/pulls/112227