fix runtime error

Author: MrWangJustToDo

packages/core/src/file.ts

@@ -87,6 +87,8 @@ export class File {
 
     this.ast = _highlighter.getAST(this.raw, this.fileName, this.lang);
 
+    if (!this.ast) return;
+
     const { syntaxFileObject, syntaxFileLineNumber } = _highlighter.processAST(this.ast);
 
     this.syntaxFile = syntaxFileObject;

packages/lowlight/src/index.ts

@@ -4,6 +4,7 @@ import { processAST, type SyntaxLine } from "./processAST";
 
 const lowlight = createLowlight(all);
 
+// !SEE https://github.com/highlightjs/highlightjs-vue
 lowlight.register("vue", function hljsDefineVue(hljs) {
   return {
     subLanguage: "xml",