message: fixed an indexing bug in mg->assembleMatCombo()
diff: @@ -500,7 +500,7 @@ void TACSMg::assembleMatCombo( ElementMatrixType matTypes[],
  }
  }
  else if (assembler[i]){
  - assembler[i]->assembleMatCombo(matTypes, scale, nmats, mat[0], matOr);
  + assembler[i]->assembleMatCombo(matTypes, scale, nmats, mat[i], matOr);
  }
  }
  