core: Error adding entities for domain cover with platform somfy_mylink

The problem

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 382, in async_add_entities
    await asyncio.gather(*tasks)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 614, in _async_add_entity
    await entity.add_to_platform_finish()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 773, in add_to_platform_finish
    self.async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 530, in async_write_ha_state
    self._async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 563, in _async_write_ha_state
    state = self._stringify_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 536, in _stringify_state
    if (state := self.state) is None:
  File "/usr/src/homeassistant/homeassistant/components/cover/__init__.py", line 240, in state
    if (closed := self.is_closed) is None:
  File "/usr/src/homeassistant/homeassistant/components/cover/__init__.py", line 293, in is_closed
    return self._attr_is_closed
AttributeError: 'SomfyShade' object has no attribute '_attr_is_closed'
2022-02-04 11:13:11 ERROR (MainThread) [homeassistant.components.cover] Error while setting up somfy_mylink platform for cover
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 257, in _async_setup_platform
    await asyncio.gather(*pending)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 382, in async_add_entities
    await asyncio.gather(*tasks)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 614, in _async_add_entity
    await entity.add_to_platform_finish()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 773, in add_to_platform_finish
    self.async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 530, in async_write_ha_state
    self._async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 563, in _async_write_ha_state
    state = self._stringify_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 536, in _stringify_state
    if (state := self.state) is None:
  File "/usr/src/homeassistant/homeassistant/components/cover/__init__.py", line 240, in state
    if (closed := self.is_closed) is None:
  File "/usr/src/homeassistant/homeassistant/components/cover/__init__.py", line 293, in is_closed
    return self._attr_is_closed
AttributeError: 'SomfyShade' object has no attribute '_attr_is_closed'

What version of Home Assistant Core has the issue?

core-2022.2.1

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant Container

Integration causing the issue

Somfy Mylink

Link to integration documentation on our website

https://www.home-assistant.io/integrations/somfy_mylink/

Example YAML snippet

No response

Anything in the logs that might be useful for us?

No response

Additional information

No response