apply the suggested patch

Author: xppt

src/symbolize.cc

@@ -647,12 +647,7 @@ OpenObjectFileContainingPcAndGetStartAddress(uint64_t pc,
     out_file_name[out_file_name_size - 1] = '\0';
 
     // Finally, "cursor" now points to file name of our interest.
-    FileDescriptor object_fd{
-        FailureRetry([cursor] { return open(cursor, O_RDONLY); })};
-    if (!object_fd) {
-      return nullptr;
-    }
-    return object_fd;
+    return FileDescriptor{FailureRetry([cursor] { return open(cursor, O_RDONLY); })};
   }
 }