Only create sensors if the station actually has values for them. (#20643)

Because Luftdaten assigns separate ids for particle and weather
measurements, most if not all stations added with config flow will
have non-functional sensors, as mentioned in #19591. This change
prevents the creation of sensors without data.

homeassistant/components/luftdaten/config_flow.py

@@ -4,7 +4,9 @@ from collections import OrderedDict
 import voluptuous as vol
 
 from homeassistant import config_entries
-from homeassistant.const import CONF_SCAN_INTERVAL, CONF_SHOW_ON_MAP
+from homeassistant.const import (
+    CONF_MONITORED_CONDITIONS, CONF_SCAN_INTERVAL,
+    CONF_SENSORS, CONF_SHOW_ON_MAP)
 from homeassistant.core import callback
 from homeassistant.helpers import aiohttp_client
 import homeassistant.helpers.config_validation as cv
@@ -77,6 +79,13 @@ class LuftDatenFlowHandler(config_entries.ConfigFlow):
         if not valid:
             return self._show_form({CONF_SENSOR_ID: 'invalid_sensor'})
 
+        available_sensors = [x for x in luftdaten.values
+                             if luftdaten.values[x] is not None]
+
+        if available_sensors:
+            user_input.update({
+                CONF_SENSORS: {CONF_MONITORED_CONDITIONS: available_sensors}})
+
         scan_interval = user_input.get(
             CONF_SCAN_INTERVAL, DEFAULT_SCAN_INTERVAL)
         user_input.update({CONF_SCAN_INTERVAL: scan_interval.seconds})