Solver: Remove DM from Vecs used in MatNullSpace
- This avoids a reference cycle
Field: Setup DM field objects
Merge commit '2bae13870c3a01dd4a1acceca3c441956f78eb01' into maint

* commit '2bae13870c3a01dd4a1acceca3c441956f78eb01':
  Field: Setup DM field objects
  Solver: Remove DM from Vecs used in MatNullSpace - This avoids a reference cycle