Fix init for first added shelly device

[mib1185]

Proposed change

This PR should fix 07a2528 in case of first shelly device ever is added.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
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• This PR fixes or closes issue: fixes #
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• The code change is tested and works locally.
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[mib1185]

This error was thrown before, when adding the first shelly device:

2021-03-27 17:58:56 ERROR (MainThread) [homeassistant.config_entries] Error setting up entry shellyplug-s-B4FD74 for shelly
Traceback (most recent call last):
  File "/home/mib85/git/homeassistant-core/homeassistant/config_entries.py", line 248, in async_setup
    result = await component.async_setup_entry(hass, self)  # type: ignore
  File "/home/mib85/git/homeassistant-core/homeassistant/components/shelly/__init__.py", line 78, in async_setup_entry
    if entry.entry_id not in device_entry.config_entries:
AttributeError: 'NoneType' object has no attribute 'config_entries'

[bieniu]

I fixed one issue and created another 🤦
LGTM, thanks!

[frenck]

Tested locally, makes all the difference!

Not joking: I added a Shelly device to my production instance and gave up... This fixes it 😬