fix: say the camera catalog has no cameras rather than none exist

An empty camera answer outside the catalog's regions read as "0 public
cameras", as if the area had none. It now says the catalog has no cameras
there.

src/tools/queries/media.test.mjs

@@ -321,4 +321,8 @@ test('an area the catalog trimmed away entirely is not reported complete', async
     area: { lat: 40.7, lon: -74, radius_km: 3 },
   });
   assert.equal(elsewhere.data.complete, true);
+  assert.equal(
+    elsewhere.summary,
+    'The camera catalog has no cameras in 3 km around 40.700, -74.000.',
+  );
 });