fix: frontmatter coercion (empty string is falsy)

Jacky Zhao

2023-12-09 2c69b0c97d40f76363d20478cb799ce4b7518e56

 quartz/plugins/transformers/index.ts

@@ -8,3 +8,4 @@
export { OxHugoFlavouredMarkdown } from "./oxhugofm"
export { SyntaxHighlighting } from "./syntax"
export { TableOfContents } from "./toc"
export { HardLineBreaks } from "./linebreaks"