don't run postprocessor in wrong formats

Author: cscheid

src/command/render/pandoc.ts

@@ -433,7 +433,9 @@ export async function runPandoc(
     postprocessors.push(...(extras.postprocessors || []));
 
     // Fix H1 title inconsistency
-    htmlPostprocessors.push(canonicalizeTitlePostprocessor);
+    if (isHtmlFileOutput(options.format.pandoc)) {
+      htmlPostprocessors.push(canonicalizeTitlePostprocessor);
+    }
 
     // add a keep-source post processor if we need one
     if (