Fix errors if rest source becomes unavailable (#24986)

* Fix errors if rest source becomes unavailable

* Remove exclamation mark

homeassistant/components/scrape/sensor.py

@@ -109,6 +109,9 @@ class ScrapeSensor(Entity):
     def update(self):
         """Get the latest data from the source and updates the state."""
         self.rest.update()
+        if self.rest.data is None:
+            _LOGGER.error("Unable to retrieve data")
+            return
 
         from bs4 import BeautifulSoup