crash of az interactive while updating vnet

## Describe the bug

**Command Name**
network vnet update --name XY -vnet --resource-group ABC --address-prefixes "10.0.0.0/16" "ace:cab:deca::/48"

**Errors:**
```
not enough values to unpack (expected 2, got 0)
Traceback (most recent call last):
pip-install-yf22vmg2\knack\knack\cli.py, ln 215, in invoke
cli\core\commands\__init__.py, ln 654, in execute
cli\core\commands\__init__.py, ln 718, in _run_jobs_serially
cli\core\commands\__init__.py, ln 711, in _run_job
Temp\pip-install-yf22vmg2\six\six.py, ln 703, in reraise
cli\core\commands\__init__.py, ln 688, in _run_job
...
b_flag, c_flag, outside, cmd = self._special_cases(cmd, outside)
interactive\azext_interactive\azclishell\app.py, ln 518, in _special_cases
cmd, continue_flag = self.handle_example(cmd, continue_flag)
ValueError: not enough values to unpack (expected 2, got 0)
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

The following command leads to the above stack trace if I'm in interactive mode.
az network vnet update --name XY -vnet --resource-group ABC --address-prefixes "10.0.0.0/16" "ace:cab:deca::/48"

Without the interactive mode, the command works fine.

## Expected Behavior
It should work in interactive mode as well.

## Environment Summary
```
Windows-10-10.0.18362-SP0
Python 3.6.6
Installer: MSI

azure-cli 2.6.0

Extensions:
interactive 0.4.4

```
## Additional Context