title: Cannot read property 'removeCls' of null for tagfield in ExtJS 5
body: <p>I'm upgrading my <code>ExtJs</code> application <code>form 4 to 5.1</code> . Initially I was using <code>boxselect</code> component from <code>UX</code>, but in <code>ExtJS 5.1</code> this component come in core Ext directory. So I removed boxselect and replaced with tagfield as said in up gradation guide. But after doing this I start getting this error </p>
  
  <blockquote>
    <p>Uncaught TypeError: Cannot read property 'removeCls' of null.</p>
  </blockquote>
  
  <p>If I rename tagfield with combo it work without any error. </p>
  
  <p>I am changing <code>xtype : ''</code> only, nothing else, don't know exactly what else I missing in upgrading <code>boxselect to tagfield in extjs 5</code> ?</p>
  
  <p>Edit -:
  After debuging more I found problem in <code>toggleInvalidCls()</code> method from <code>Ext.form.field.Text</code>..Please find code bellow,</p>
  
  <pre><code>toggleInvalidCls: function(hasError) {
      var method = hasError ? 'addCls' : 'removeCls';
      this.callParent();
      this.triggerWrap[method](this.triggerWrapInvalidCls);//getting error here
      this.inputWrap[method](this.inputWrapInvalidCls);
  },
  </code></pre>
  
  <p>this.triggerWrap object coming null for tagfield...any reason ?
  Brwoser console also showing warning <code>XTemplate evaluation exception: wrapperStyle is not defined</code> before throwing error of removeCls...</p>