Guard against nullable filename in is_eslint

config/helpers/is_eslint.js

@@ -5,7 +5,7 @@ const isESLint = mod => {
   let parent = mod.parent;
 
   while (parent) {
-    if (parent.filename.includes('/eslint')) {
+    if (parent.filename && parent.filename.includes('/eslint')) {
       return true;
     }