message: remove unnecessary casting to csr matrix, which resulted in a segmentation fault
diff: @@ -145,7 +145,7 @@ protected:
  stop::combine(std::move(parameters_.criteria));
  using CsrMatrix = matrix::Csr<ValueType, IndexType>;
  -
  + /*
  GKO_ASSERT_IS_SQUARE_MATRIX(system_matrix);
  // This is needed because it does not make sense to call the copy and
  // convert if the existing matrix is empty.
  @@ -155,7 +155,7 @@ protected:
  } else {
  system_matrix_ =
  copy_and_convert_to<CsrMatrix>(exec, system_matrix);
  - }
  + }*/
  }
  private:
  