I'm getting a new build error with Sencha Cmd v3.0.0.190 and ST 2.1rc1.

Code:
[INFO ]		Compiling app.js and dependencies
[INFO ]		Processing classPath entry : /project/sencha-compile-temp-dir
[INFO ]		Processing classPath entry : /project/touch/src
[INFO ]		Processing classPath entry : /project/app.js
[INFO ]		Processing classPath entry : /project/MyAppDir
[INFO ]		Processing classPath entry : /project/lib
[WARN ]		[ [1000] : Yui Compressor Warning <> Trailing comma is not legal in an ECMA-262 object initializer => }, function() { ] :: ( /project/touch/src/app/Controller.js => 625 : 1 )
[ERROR]		def was null
[ERROR]		failed to find meta class definition for name reader.null
[ERROR]		Exception running app build : JavaException: com.sencha.exceptions.BasicException: null
[ERROR]		javax.script.ScriptException: sun.org.mozilla.javascript.internal.JavaScriptException: [object Error] (<Unknown source>#709) in <Unknown source> at line number 709
I have a custom application directory (MyAppDir), and another directory (lib) for other classes. I edited .sencha/app/sencha.cfg as follows:

Code:
app.classpath=${app.dir}/app.js,${app.dir}/MyAppDir,${app.dir}/lib
How would I go about debugging this? I'm not sure where it's trying to look up "reader.null".