Do not allow error if docs do not exist

doc/docusaurus/build.sh

doc/docusaurus/docs/about.md

doc/docusaurus/docs/api.md

doc/docusaurus/docs/community.md

doc/docusaurus/docs/input_data.md

doc/docusaurus/docs/install_use.md

doc/docusaurus/docs/math_expr.md

doc/docusaurus/docs/math_model.md

doc/docusaurus/docs/param_tree.md

doc/docusaurus/docs/participate.md