Field Editor ribbon button bug while in Preview Mode

During a demo, I was in Preview mode in Page Editor discussing some changes.   I unknowingly tried to edit a hidden field using a Field Editor button I created to manage the meta data while in preview mode, and the results were not what I expected.

Not only could I click the ribbon button, I could also see the fields and make it appear as if I could edit them. 

Thinking I was in fact in Edit mode, I clicked ok on the popup.  I was left with a non-responsive Sitecore. 

I had to refresh the page to get the page to respond again.  

I created a simple patch for this, where it checks the mode of the page and sets the CommandState to disabled if it is in preview mode.  

C# code for the fix:

    [Serializable]
    public class FieldEditor : Sitecore.Shell.Applications.WebEdit.Commands.FieldEditor
    {
        public override CommandState QueryState(CommandContext context)
        {
            Assert.ArgumentNotNull(context, "context");
            return WebUtil.GetQueryString("mode") == "preview" || (context.Items.Length > 0 && context.Items[0] != null && !context.Items[0].Access.CanWrite()) ? CommandState.Disabled : CommandState.Enabled;
        }
    }

Config file patch:

 <sitecore>
    <commands>
      <command name="webedit:fieldeditor" type="Sitecore.Shell.Applications.WebEdit.Commands.FieldEditor, Sitecore.Client">
        <patch:attribute name="type">Namespace.Commands.FieldEditor, Namespace</patch:attribute>
      </command>
    </commands>
 </sitecore>

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