Looks like we can't reproduce the issue or there's a problem in the test case provided.
TypeError: 'null' is not a constructor (evaluating 'new c(a)') with blank project
1- I start a blank new EXTJS 4.0 project with Sencha Designer 2 Build: 311.
2- I drag a Store in "Stores"
3- I save and deploy
I get TypeError: 'null' is not a constructor (evaluating 'new c(a)') in my browser console. I use Safari 5.1.4
I tried everything I could and always get this error.
How can I fix this?
Can you archive your project and attach it here so we can have a look.
File -> Archive Project
here it is.
If you find the bug please reply.
update: coming from the Sencha Touch 2 world, I didn't know EXT4 project needed to be run under a web server (Touch projects can be accessed through file:/// and they run). So I started a webserver with "python -m SimpleHTTPServer" and got it to work.