Fix env bug

Author: jeromewu

src/browser/defaultOptions.js

@@ -5,7 +5,7 @@ const { devDependencies } = require('../../package.json');
  * Default options for browser environment
  */
 module.exports = {
-  corePath: (typeof process !== 'undefined' && process.env.FFMPEG_ENV === 'development')
+  corePath: process.env.NODE_ENV === 'development'
     ? resolveURL('/node_modules/@ffmpeg/core/dist/ffmpeg-core.js')
     : `https://unpkg.com/@ffmpeg/core@${devDependencies['@ffmpeg/core'].substring(1)}/dist/ffmpeg-core.js`,
 };