dayjs through error for null and empty values

[nageshwar521]

Describe the bug
Migrating from moment js to dayjs, Facing many issues... Really getting irritated about the behavior of dayjs... I am working on the antd time picker, its showing Invalid Value except for the static time string...

Expected behavior
A clear and concise description of what you expected to happen.

Information

• Day.js Version [e.g. v1.0.0]
• OS: [e.g. iOS]
• Browser [e.g. chrome 62]
• Time zone: [e.g. GMT-07:00 DST (Pacific Daylight Time)]