System Information
Win7 64bit
Blender Version
Broken: 2.78c
Short description of error
Bevel doesn't correctly work with default empty Vgroup, until manually click Assign in edit mode
Exact steps for others to reproduce the error
Load default scene
Click "+" button to create Vgroup
Add Bevel modifier to the cube and switch to Vgroup method
Choose Vgroup you have created-> Bevel is working, but shouldn't
This is actually a bug in our defvert_array_find_weight_safe(), which was assuming that having a valid vgroup index but NULL vgroup data pointer was same as not having a valid vgroup index, and was returning '1.0' in both cases.
This is wrong, invalid vgroup index means the vgroup selected is invalid, does not exists, in that case it is OK to return 1.0 (i.e. maximum weight, as if no vgroup was selected).
But in case of valid vgroup and NULL vgroup data pointer, only means that vgroup is valid, and just totally empty, so we shall return '0.0' value then!