pofs is guaranteed to be non-nullptr after getOutputStream, so no need
to check that. is_open() only matters to decide if close() is needed.

V595 The 'pofs' pointer was utilized before it was verified against nullptr.
     Check lines: 1033, 1057.
     Check lines: 1194, 1220.

Change-Id: I2dd22d29c465889269f2496f0964bee030cb5964
Reviewed-on: https://gerrit.libreoffice.org/71456
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>