Function assertIsNull

assertIsNull(input: unknown, error?: string | Error): asserts input is null
Assert that input is null.
Parameters
- input: unknown
- error: string | Error = 'input is not null'
Returns asserts input is null
Example
```
assertIsNull(null); // does not throw
assertIsNull(undefined); // throws TypeError: input is not null
```
- Defined in src/assertion/assertIsNull.ts:14