Check against invalid TextEditors

Guard against invalid `TextEditor`s, and ones without a path.

Fixes #162.

Author: Arcanemagus

lib/index.js

@@ -51,15 +51,23 @@ export function provideLinter() {
     scope: 'file',
     lintOnFly: true,
     lint: async (editor) => {
-      const { HTMLHint } = require('htmlhint');
+      if (!atom.workspace.isTextEditor(editor)) {
+        return null;
+      }
 
-      const fileText = editor.getText();
       const filePath = editor.getPath();
+      if (!filePath) {
+        // Invalid path
+        return null;
+      }
 
+      const fileText = editor.getText();
       if (!fileText) {
         return [];
       }
 
+      const { HTMLHint } = require('htmlhint');
+
       const ruleset = await getConfig(filePath);
 
       const messages = HTMLHint.verify(fileText, ruleset || undefined);