Install Demo Error

I get this error while installing demo

Simulating 2019-08-15: Day 0Traceback (most recent call last):
  File "/usr/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 97, in <module>
    main()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 18, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/__init__.py", line 25, in _func
    ret = f(frappe._dict(ctx.obj), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/utils.py", line 145, in execute
    ret = frappe.get_attr(method)(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/demo/demo.py", line 79, in simulate
    purchase.work()
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/demo/user/purchase.py", line 97, in work
    make_subcontract()
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/demo/user/purchase.py", line 148, in make_subcontract
    po.insert()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 229, in insert
    self.run_before_save_methods()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 888, in run_before_save_methods
    self.run_method("validate")
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 787, in run_method
    out = Document.hook(fn)(self, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 1058, in composer
    return composed(self, method, *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 1041, in runner
    add_to_return_value(self, fn(self, *args, **kwargs))
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/document.py", line 781, in <lambda>
    fn = lambda self, *args, **kwargs: getattr(self, method)(*args, **kwargs)
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/buying/doctype/purchase_order/purchase_order.py", line 58, in validate
    self.validate_bom_for_subcontracting_items()
  File "/home/frappe/frappe-bench/apps/erpnext/erpnext/buying/doctype/purchase_order/purchase_order.py", line 118, in validate_bom_for_subcontracting_items
    .format(item.item_code, item.idx)))
  File "/home/frappe/frappe-bench/apps/frappe/frappe/__init__.py", line 360, in throw
    msgprint(msg, raise_exception=exc, title=title, indicator='red')
  File "/home/frappe/frappe-bench/apps/frappe/frappe/__init__.py", line 346, in msgprint
    _raise_exception()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/__init__.py", line 315, in _raise_exception
    raise raise_exception(msg)
frappe.exceptions.ValidationError: BOM is not specified for subcontracting item Base Plate at row 1