message: Fix smv filter
diff: @@ -216,9 +216,9 @@ breathe_default_project = "CCF"
  # Set up multiversion extension
  -smv_tag_whitelist = ""
  +smv_tag_whitelist = None
  smv_branch_whitelist = r"^(main)|(release\/([2-9]|\d\d\d*)\.x)$"
  -smv_remote_whitelist = ""
  +smv_remote_whitelist = None
  smv_outputdir_format = "{ref.name}"
  assert re.match(smv_branch_whitelist, "main")
  