Versions: 0.7.13 with Sencha Touch 2.1.1
Browser: Chrome 25 (Win8 / Desktop)
Severity: major

When using Sencha.io, the Ext.data.Store sync override will not execute the callback if the store proxy.sync is undefined. Can happen when using local storage or if the store has no proxy. This can be problematic if the application do important things (checks, UI modification, etc.) in this callback. I don't understand why the original Ext.data.Store.sync method doesn't provide this callback feature (but that is a ST topic).

I don't have test case, but your sync override implementation (cf/Overrides.js, line 15) is clear enough:
Code:
    sync: function(callback,scope) {
        if (typeof(this.getProxy().sync) === "undefined") {
            return this.storeSync();
        }else{
            return this.getProxy().sync(this,callback,scope);
        }
    }
Patch

I explicitly call the callback with 'ok':
Code:
    sync: function(callback,scope) {
        if (typeof(this.getProxy().sync) === "undefined") {
            var result = this.storeSync();
            if(callback) {
                callback.call(scope, {r: 'ok'});
            }
            return result;
        }else{
            return this.getProxy().sync(this,callback,scope);
        }
    }
I think that the callback parameters can also be dependent to the storeSync() returned value (here result). Not sure you need a patch for this modification but I can create one over 0.7.13 if you want.