Uncaught TypeError: Cannot call method 'substring' of undefined ext-all-debug.js:3487

[awhitford]

In my Ext3 to Ext4 migration, I am left with a killer that I do not understand:

Uncaught TypeError: Cannot call method 'substring' of undefined
Manager.Ext.ClassManager.parseNamespace  ext-all-debug.js:3487
Manager.Ext.ClassManager.get  ext-all-debug.js:3583
Manager.Ext.ClassManager.instantiate  ext-all-debug.js:3749
Manager.Ext.ClassManager.instantiateByAlias  ext-all-debug.js:3737
(anonymous function)  ext-all-debug.js:1537
(anonymous function)  ext-all-debug.js:1521
Ext.define.create  ext-all-debug.js:16667
Ext.define.createComponent  ext-all-debug.js:28187
Ext.define.lookupComponent  ext-all-debug.js:28175
Ext.define.prepareItems  ext-all-debug.js:28146
Ext.define.addDocked  ext-all-debug.js:32932
Ext.define.bridgeToolbars  ext-all-debug.js:37435
Ext.define.initComponent  ext-all-debug.js:37312
Base.callParent  ext-all-debug.js:2833
Ext.define.initComponent  ext-all-debug.js:74857
(anonymous function)  ext-all-debug.js:1537
Base.callParent  ext-all-debug.js:2833
Ext.define.initComponent  ext-all-debug.js:76456
(anonymous function)  ext-all-debug.js:1537
Ext.define.constructor  ext-all-debug.js:18576
Base.callParent  ext-all-debug.js:2833
Ext.define.constructor  ext-all-debug.js:27217
(anonymous function)  ext-all-debug.js:1537
Ext.Class.Class.newClass  ext-all-debug.js:3067
anonymous:2
Manager.Ext.ClassManager.instantiate  ext-all-debug.js:3787
Manager.Ext.ClassManager.instantiateByAlias  ext-all-debug.js:3737
(anonymous function)  ext-all-debug.js:1537
(anonymous function)  ext-all-debug.js:1521
Ext.define.create  ext-all-debug.js:16667
Ext.define.createComponent  ext-all-debug.js:28187
Ext.define.lookupComponent  ext-all-debug.js:28175
Ext.define.prepareItems  ext-all-debug.js:28146
Ext.define.add  ext-all-debug.js:28235
Ext.define.add  ext-all-debug.js:28225
Ext.define.initItems  ext-all-debug.js:28065
Ext.define.initComponent  ext-all-debug.js:28049
(anonymous function)  ext-all-debug.js:1537
Base.callParent  ext-all-debug.js:2833
Ext.define.initComponent  ext-all-debug.js:60633
AutosysAdminViewportUi.Ext.extend.initComponent  MyViewport.ui.js:348
AutosysAdminViewport.Ext.extend.initComponent  MyViewport.js:134
Ext.define.constructor  ext-all-debug.js:18576
Base.callParent  ext-all-debug.js:2833
Ext.define.constructor  ext-all-debug.js:27217
Ext.Class.Class.newClass  ext-all-debug.js:3067
(anonymous function)  MyViewport.js:140
isEvent  ext-all-debug.js:10117
call  ext-all-debug.js:10073

I traced this further down to the offending component, a paging toolbar. Its config is simply:

        bbar: {
          xtype: 'paging',
          pageSize: 50,
          store: myStore,
          displayInfo: true
        }

What could be wrong?