fix: check if filename exists before processing

Author: micantoine

src/index.ts

@@ -35,11 +35,14 @@ let pluginOptions: PluginOptions;
  * @returns the preprocessor markup
  */
 const markup: MarkupPreprocessor = async ({ content, filename }) => {
-  const isIncluded = filename ? isFileIncluded(pluginOptions.includePaths, filename) : false;
-
-  if (!isIncluded || (!pluginOptions.parseStyleTag && !pluginOptions.parseExternalStylesheet)) {
+  if (
+    !filename ||
+    !isFileIncluded(pluginOptions.includePaths, filename) ||
+    (!pluginOptions.parseStyleTag && !pluginOptions.parseExternalStylesheet)
+  ) {
     return { code: content };
   }
+
   let ast: Ast;
   try {
     ast = parse(content, { filename });
@@ -61,7 +64,7 @@ const markup: MarkupPreprocessor = async ({ content, filename }) => {
   let { mode, hashSeeder } = pluginOptions;
 
   if (pluginOptions.parseStyleTag && hasModuleAttribute(ast)) {
-    const moduleAttribute = ast.css.attributes.find((item) => item.name === 'module');
+    const moduleAttribute = ast.css?.attributes.find((item) => item.name === 'module');
     mode = moduleAttribute.value !== true ? moduleAttribute.value[0].data : mode;
   }