title: EXTJS: hidden element does not show up after setvisible
body: <p>Hello I want to show and image that is like an alert sign when a change is done, then I have a footer panel like this one, with the sign:</p>
  
  <pre><code>Ext.define('footerPanel', {
      extend: 'Ext.panel.Panel',
      cls: 'fastec_background',
      height: 24,
      autoScroll: false,
      border: false,
      layout: {
          type: 'border'
      },
      id: 'panel_footerFastec',
  
  
      initComponent: function () {
          var me = this;
  
  
          Ext.applyIf(me, {
              items: [{
                  margin: '5 5 0 20',
                  xtype: 'label',
                  region: 'center',
                  html: '&lt;a&gt;© 2012 FASTEC GmbH, Paderborn, Germany - &lt;/a&gt;&lt;a target="_blank" href="http://www.easyoee.de"&gt;www.easyOEE.de&lt;/a&gt; &lt;a target="_blank" href="http://www.fastec.de"&gt;www.fastec.de&lt;/a&gt;'
              }, {
                  xtype: 'container',
                  region: 'east',
                  layout: 'table',
                  id: 'cont_footer_icons',
                  items: [{
                      xtype: 'image',
                      id: 'configchangedIcon',
                      height: 16,
                      margin: '5 0 5 0',
                      width: 16,
                      maxHeight: 20,
                      dock: 'right',
                      maxWidth: 20,
                      scale: 'large',
                      src: 'files/images/disk_blue.png',
                      hidden: true
                  }, {
                      xtype: 'image',
                      height: 16,
                      id: 'errorIcon',
                      margin: '5 0 5 0',
                      width: 16,
                      dock: 'right',
                      maxHeight: 20,
                      maxWidth: 20,
                      scale: 'large',
                      src: 'files/images/error16.gif',
                      hidden: true
                  }]
              }]
          });
  
  
          me.callParent(arguments);
      }
  });
  </code></pre>
  
  <p>And the idea is that I have a general function which I could call anywhere and show or hide the icon, but unfortunately I call this function and nothing happens:</p>
  
  <pre><code>changeIconVisibility = function(str, value) {
      try {
          switch(str){
              case 'configchangedIcon':
                  var img = Ext.getCmp('configchangedIcon');
                  if(value){
                      img.setVisible(true);
                  }else{
                      img.setVisible(false);
                  }
              break;
          }
      } catch (e) {
          Ext.msg.alert(e);
      }
  }
  </code></pre>
  
  <p>I tried by directly calling the component and setVisible(true) as well and nothing happens.</p>