fix: remove fallback cover path and throw error for missing cover

src/index.ts

@@ -50,7 +50,8 @@ async function get_image_from_server(
           first_error,
           secong_error,
         );
-        resultFilePath = "public/covers/0.png";
+        // resultFilePath = "public/covers/0.png";
+        throw Error("cover not found");
       }
     }
   }