Fix HomeKit linked battery sensor crash (#28974)

* fix homekit linked battery sensor crash

* simplified missing linked battery

* fixed formatting

* Make if faster

homeassistant/components/homekit/accessories.py

@@ -105,8 +105,18 @@ class HomeAccessory(Accessory):
         battery_found = self.hass.states.get(self.entity_id).attributes.get(
             ATTR_BATTERY_LEVEL
         )
+
         if self.linked_battery_sensor:
-            battery_found = self.hass.states.get(self.linked_battery_sensor).state
+            state = self.hass.states.get(self.linked_battery_sensor)
+            if state is not None:
+                battery_found = state.state
+            else:
+                self.linked_battery_sensor = None
+                _LOGGER.warning(
+                    "%s: Battery sensor state missing: %s",
+                    self.entity_id,
+                    self.linked_battery_sensor,
+                )
 
         if battery_found is None:
             return

tests/components/homekit/test_accessories.py

@@ -245,6 +245,33 @@ async def test_linked_battery_sensor(hass, hk_driver, caplog):
     assert acc._char_charging.value == 0
 
 
+async def test_missing_linked_battery_sensor(hass, hk_driver, caplog):
+    """Test battery service with mising linked_battery_sensor."""
+    entity_id = "homekit.accessory"
+    linked_battery = "sensor.battery"
+    hass.states.async_set(entity_id, "open")
+    await hass.async_block_till_done()
+
+    acc = HomeAccessory(
+        hass,
+        hk_driver,
+        "Battery Service",
+        entity_id,
+        2,
+        {CONF_LINKED_BATTERY_SENSOR: linked_battery},
+    )
+    acc.update_state = lambda x: None
+    assert not acc.linked_battery_sensor
+
+    await hass.async_add_job(acc.run)
+    await hass.async_block_till_done()
+
+    assert not acc.linked_battery_sensor
+    assert not hasattr(acc, "_char_battery")
+    assert not hasattr(acc, "_char_low_battery")
+    assert not hasattr(acc, "_char_charging")
+
+
 async def test_call_service(hass, hk_driver, events):
     """Test call_service method."""
     entity_id = "homekit.accessory"