Running this command "bench --site IP_ADDRESS install-app erpnext"

Traceback (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/ahmadi/frappe_benchV12/apps/frappe/frappe/utils/bench_helper.py", line 97, in <module>
    main()
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/utils/bench_helper.py", line 18, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/env/lib/python3.5/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/commands/__init__.py", line 25, in _func
    ret = f(frappe._dict(ctx.obj), *args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/commands/site.py", line 179, in install_app
    _install_app(app, verbose=context.verbose)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/installer.py", line 83, in install_app
    sync_for(name, force=True, sync_everything=True, verbose=verbose, reset_permissions=True)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/sync.py", line 56, in sync_for
    reset_permissions=reset_permissions, for_sync=True)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/modules/import_file.py", line 66, in import_file_by_path
    ignore_version=ignore_version, reset_permissions=reset_permissions)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/modules/import_file.py", line 106, in import_doc
    doc = frappe.get_doc(docdict)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/__init__.py", line 753, in get_doc
    doc = frappe.model.document.get_doc(*args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/document.py", line 71, in get_doc
    return controller(*args, **kwargs)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/document.py", line 115, in __init__
    super(Document, self).__init__(kwargs)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 65, in __init__
    self.update(d)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 88, in update
    self.set(key, value)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 135, in set
    self.extend(key, value)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 172, in extend
    self.append(key, v)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 149, in append
    value = self._init_child(value, key)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 184, in _init_child
    value["doctype"] = self.get_table_field_doctype(key)
  File "/home/ahmadi/frappe_benchV12/apps/frappe/frappe/model/base_document.py", line 298, in get_table_field_doctype
    return self.meta.get_field(fieldname).options
AttributeError: 'NoneType' object has no attribute 'options'

I got this outcome as the result of running “bench --site IP_ADDRESS install-app erpnext”, Can any one of you help me out what I get this outcome ? Thank you a lot! I am so overwhelmed! Pleas help me out

Is this a new installation and first time running that command or have you been using this instance and installed erpnext to other sites?

What is the operating environment and version of ERPnext and frappe?

yeah, This is my first time for me to install Frappe and ERPNext. It’s on a ubuntu cloud server 16.04 with 2GB RAM. The bench version is 5.00 but the Frappe and ERPNext have not been installed yet