Providing empty string to disable dsym upload gives error

[EddieCameron]

When providing an empty string to override the default env var DSYM_OUTPUT_PATH, the plugin complains that the path is invalid.
It looks like the check whether to upload the dSYM is just checking for a nil dsym_file string, but the string can never be nil since it would be defaulted to the DSYM_OUTPUT_PATH.

if dsym_file
          dsym_file_basename = File.basename(dsym_file)
          dsym_file_name = "#{url_part}#{dsym_file_basename}"

          dsym_file_data = File.open(dsym_file, 'rb')

          dsym_url = self.upload_file(s3_client, s3_bucket, app_directory, dsym_file_name, dsym_file_data, acl, server_side_encryption, download_endpoint, download_endpoint_replacement_regex)

          # Setting action and environment variables
          Actions.lane_context[SharedValues::S3_DSYM_OUTPUT_PATH] = dsym_url
          ENV[SharedValues::S3_DSYM_OUTPUT_PATH.to_s] = dsym_url
end