某些用户存在Products中name为None条目，导致显示出问题

[AlexGuo1998]

Describe the bug / 描述 bug
添加某用户后，BaiduPCS-Py userlist 输出 AttributeError: 'NoneType' object has no attribute 'startswith'，其余用户管理指令（userdel、su）也无法使用

To Reproduce / 复现问题

1. BaiduPCS-Py useradd ...
2. BaiduPCS-Py userlist

Screenshots / 问题截图
N/A

Envrionment / 运行环境

• OS: Linux Ubuntu 20.04
• Python 3.8.5
• BaiduPCS-Py v0.6.13

Runing log / 运行日志

2021-03-19 01:13:15,178 | DEBUG | app: `app`: System Error: Traceback (most recent call last):
  File "/home/alex/miniconda3/lib/python3.8/site-packages/baidupcs_py/app/app.py", line 101, in wrap
    return func(*args, **kwargs)
  File "/home/alex/miniconda3/lib/python3.8/site-packages/baidupcs_py/app/app.py", line 427, in userlist
    display_user_infos(*ls, recent_user_id=am._who)
  File "/home/alex/miniconda3/lib/python3.8/site-packages/baidupcs_py/commands/display.py", line 408, in display_user_infos
    if p.name.startswith("svip2_nd"):
AttributeError: 'NoneType' object has no attribute 'startswith'

Additional context / 补充内容
在 baidupcs_py/commands/display.py 中 display_user_infos

BaiduPCS-Py/baidupcs_py/commands/display.py

Lines 405 to 413 in 6fe1f21

	assert products
	for p in products or []:
	avail = str(datetime.timedelta(seconds=(int(p.end_time - time.time()))))
	if p.name.startswith("svip2_nd"):
	svip = f"Left [green]{avail}[/green]"
	continue
	if p.name.startswith("contentvip_nd"):
	vip = f"Left [green]{avail}[/green]"
	continue

>>> print(products)
[
    PcsUserProduct(name='offlinedl_permanent', start_time=1613264983, end_time=2147483648),
    PcsUserProduct(name=None, start_time=1615737599, end_time=1616342399),
    PcsUserProduct(name='svip2_nd', start_time=1615737599, end_time=1626278399),
    PcsUserProduct(name='contentvip_nd', start_time=1615737599, end_time=1626278399)
]

应该是第二项导致出错，临时解决方案是在407行插入

if p.name is None:
    continue

[PeterDing]

已经在 v0.6.14 中修复。