Implement available property for Airthings BLE sensors (#96735)

homeassistant/components/airthings_ble/sensor.py

@@ -226,6 +226,14 @@ class AirthingsSensor(
             model=airthings_device.model,
         )
 
+    @property
+    def available(self) -> bool:
+        """Check if device and sensor is available in data."""
+        return (
+            super().available
+            and self.entity_description.key in self.coordinator.data.sensors
+        )
+
     @property
     def native_value(self) -> StateType:
         """Return the value reported by the sensor."""