Fix some IDE warnings, mostly around type safety on the Python side

solarconditionsproviders/solar_conditions_provider.py

@@ -10,6 +10,7 @@ class SolarConditionsProvider:
     def __init__(self, provider_config):
         """Constructor"""
 
+        self._solar_conditions_cache = None
         self.name = provider_config["name"]
         self.enabled = provider_config["enabled"]
         self.last_update_time = datetime.min.replace(tzinfo=pytz.UTC)