fix: explicit undefined check in header transclude

Jacky Zhao

2023-11-19 516d9a27e7e2c08efdf24857b03f1831dbaf7da7

 quartz/plugins/transformers/frontmatter.ts

@@ -37,6 +37,11 @@
              data.tags = data.tag
            }

            // coerce title to string
            if (data.title) {
              data.title = data.title.toString()
            }

            if (data.tags && !Array.isArray(data.tags)) {
              data.tags = data.tags
                .toString()