Use bat query param rather than header when streaming as headers not passed in HEAD requests from sonos. Improve handling of failures when fetching coverArt to return undefined rather than throwing exception (#59)

tests/smapi.test.ts

@@ -2471,12 +2471,9 @@ describe("api", () => {
                   getMediaURIResult: bonobUrl
                     .append({
                       pathname: `/stream/track/${trackId}`,
+                      searchParams: { "bat": accessToken }
                     })
                     .href(),
-                  httpHeaders: {
-                    header: "bat",
-                    value: accessToken,
-                  },
                 });
 
                 expect(musicService.login).toHaveBeenCalledWith(authToken);