title: Not able to run Gxt 3.1.1 application after upgrading from 3.0.0
body: <p>I have tried upgrading my projects GWT  and Gxt from 2.5.1,3.0.0 to 2.7,3.1.1 . I was able to build the project successfully with some workarounds but am not able to run it. Error I am getting is :</p>
  
  <pre><code>Loading inherited module 'com.ApplicationShellModule'
     Loading inherited module 'com.sencha.gxt.ui.GXT'
        Loading inherited module 'com.sencha.gxt.data.Data'
           Loading inherited module 'com.sencha.gxt.core.Core'
              [ERROR] Line 96: Value 'ie6' in not a valid value for property 'user.agent'
  </code></pre>
  
  <p>I am trying to find the cause in applicationShellModule.gxt.xml which is my gxt configuration which is as follows near line 96:</p>
  
  <pre><code>  &lt;property-provider name="gxt.user.agent"&gt;
      &lt;![CDATA[
      {window.alert("inside user agent gxt");
  
          var ua = navigator.userAgent.toLowerCase();
          if (ua.indexOf('trident') != -1) {
              if (11 == document.documentMode) return 'gecko1_9';
              return 'ie8';
          } 
          if (ua.indexOf('msie') != -1) {
              return 'ie8';
          } 
          return 'chrome';
      } ]]&gt;
    &lt;/property-provider&gt;
  
    &lt;property-provider name="user.agent"&gt;
      &lt;![CDATA[
      { window.alert("inside user agent");
  
      return 'ie8';
  
          var ua = navigator.userAgent.toLowerCase();
          if (ua.indexOf('trident') != -1) {
              if (11 == document.documentMode) return 'gecko1_8';
              return 'ie8';
          }
          if (ua.indexOf('msie') != -1) {
              return 'ie8';
          }
          return 'safari';
      } ]]&gt;
    &lt;/property-provider&gt;
  
    &lt;property-provider name="user.agent.os"&gt;
      &lt;![CDATA[
      {window.alert("inside user agent os");
  
          return 'windows';
      } ]]&gt;
    &lt;/property-provider&gt;
  
    &lt;!-- Supported Browsers --&gt;
  &lt;!-- uncomment this for dev after upgrade
    &lt;set-property name="gxt.user.agent" value="chrome, ie8, gecko1_9" /&gt;
    &lt;set-property name="user.agent.os" value="windows" /&gt;
    &lt;extend-property name="locale" values="en,es,ko,pt,ru,fr,hu,pl,zh_CN,zh_TW,tr,uk"/&gt;
    &lt;set-property-fallback name="locale" value="en" /&gt;
    &lt;collapse-property name="locale" values="en, default" /&gt; 
  --&gt;
  &lt;!-- changes for upgrade gwt --&gt;
  &lt;set-property name="user.agent" value="ie8,ie9,opera,gecko1_8,safari" /&gt;
  &lt;set-property name="gxt.user.agent" value="ie8" /&gt;
      &lt;set-property name="user.agent.os" value="windows" /&gt;
      &lt;extend-property name="locale" values="en" /&gt;
      &lt;set-property-fallback name="locale" value="en" /&gt;
      &lt;collapse-property name="locale" values="en" /&gt;
      &lt;collapse-all-properties /&gt;
                 &lt;set-configuration-property name="CssResource.obfuscationPrefix"
          value="empty" /&gt;
  &lt;add-linker name="xsiframe"/&gt;
  &lt;set-configuration-property name="devModeRedirectEnabled" value="true"/&gt;
  &lt;set-property name="compiler.useSourceMaps" value="true"/&gt;
  &lt;!-- upgrade changes over check last line setting to false below revert it to original--&gt;
  </code></pre>
  
  <p>I have set the user agent manually here as can be seen to a list of browsers but not ie6 which is coming under the error. I have searched for the string 'ie6' but nowhere I am getting the actual reason for this error. Please help me get out of the issue. </p>