sd-journal: data object may be invalid after data_object_in_hash_table()
    
    Fixes a bug introduced by 578cd1855b73d2710ae14a8d77c4fac1d8ea7f48.
    
    The function `data_object_in_hash_table()` calls
    `journal_file_move_to_object()` with `OBJECT_DATA`. Hence,
    previously obtained pointer to a data object may be now invalid.
    
    Fixes #23794.
    
    (cherry picked from commit b8478c14c7367c3ec5d47d2680a3390b0dedecb1)