Since ExtJS5, when doing such a declaration,

	Ext.applyIf(me, {
	    items: {
		xtype: 'pveKVComboBox',
		comboItems: data,
	    }
	});

the comboItems property is passed in the parent class as a config object,
instead of being directly available via this.comboItems

Since using a config object is the recommended way of passing parameters
int the ExtJS class model, adapt the parent class to use the new paradigm.