message: Improve logic in pbilinearform
diff: @@ -233,11 +233,14 @@ void ParBilinearForm::AssembleSharedFaces(int skip_zeros)
  void ParBilinearForm::Assemble(int skip_zeros)
  {
  - if (!ext && mat == NULL && fbfi.Size() > 0)
  + if (fbfi.Size() > 0)
  {
  pfes->ExchangeFaceNbrData();
  + if (!ext && mat == NULL)
  + {
  pAllocMat();
  }
  + }
  BilinearForm::Assemble(skip_zeros);
  