Clear miflora sensor state on exception (#29276)

* Clear state on exception

Clear state if querying the device fails. The state is then set to unknown, so it can be tracked if a miflora device isn't responding any more.

* Add available()

Signal valid data via available()

homeassistant/components/miflora/sensor.py

@@ -106,6 +106,7 @@ class MiFloraSensor(Entity):
         self._icon = icon
         self._name = name
         self._state = None
+        self._available = False
         self.data = []
         self._force_update = force_update
         # Median is used to filter out outliers. median of 3 will filter
@@ -132,6 +133,11 @@ class MiFloraSensor(Entity):
         """Return the state of the sensor."""
         return self._state
 
+    @property
+    def available(self):
+        """Return True if entity is available."""
+        return self._available
+
     @property
     def unit_of_measurement(self):
         """Return the units of measurement."""
@@ -156,15 +162,14 @@ class MiFloraSensor(Entity):
         try:
             _LOGGER.debug("Polling data for %s", self.name)
             data = self.poller.parameter_value(self.parameter)
-        except OSError as ioerr:
+        except (OSError, BluetoothBackendException) as err:
-            _LOGGER.info("Polling error %s", ioerr)
+            _LOGGER.info("Polling error %s: %s", type(err).__name__, err)
-            return
+            self._available = False
-        except BluetoothBackendException as bterror:
-            _LOGGER.info("Polling error %s", bterror)
             return
 
         if data is not None:
             _LOGGER.debug("%s = %s", self.name, data)
+            self._available = True
             self.data.append(data)
         else:
             _LOGGER.info("Did not receive any data from Mi Flora sensor %s", self.name)