Guard against empty ssdp locations (#43156)

homeassistant/components/ssdp/__init__.py

@@ -92,7 +92,10 @@ class Scanner:
 
             entries_to_process.append(entry)
 
-            if entry.location not in self._description_cache:
+            if (
+                entry.location is not None
+                and entry.location not in self._description_cache
+            ):
                 unseen_locations.add(entry.location)
 
         if not entries_to_process:

tests/components/ssdp/test_init.py

@@ -10,7 +10,7 @@ from homeassistant.components import ssdp
 from tests.common import mock_coro
 
 
-async def test_scan_match_st(hass):
+async def test_scan_match_st(hass, caplog):
     """Test matching based on ST."""
     scanner = ssdp.Scanner(hass, {"mock-domain": [{"st": "mock-st"}]})
 
@@ -38,6 +38,7 @@ async def test_scan_match_st(hass):
         ssdp.ATTR_SSDP_SERVER: "mock-server",
         ssdp.ATTR_SSDP_EXT: "",
     }
+    assert "Failed to fetch ssdp data" not in caplog.text
 
 
 @pytest.mark.parametrize(