Im getting an error on a contentpicker, when nothing is chosen in the contentpicker - The problem is that no matter what, the contentpicker always returns something:

If nothing is chosen in the contentpicker, then it still returns " umbraco.MacroEngines.DynamicXml " - So that means i can't check to see if it's empty, because it never is... So how do I do this? 

var node = Library.NodeById(page.planetLink);
                    var graphic = page.Media("planetGraphic", "umbracoFile");
                    var gWidth = page.Media("planetGraphic", "umbracoWidth")+"px";
                    var gHeight = page.Media("planetGraphic", "umbracoHeight")+"px";
                    var gPositionX = page.planetXPosition+"px";
                    var gPositionY = page.planetYPosition+"px";
                    var gZindex = page.zIndex;
                    var planetTitle = page.planetTitle;

                    if (!string.IsNullOrEmpty(page.GetPropertyValue("planetLink")))
                    {
                         <div class="planet" style="width: @gWidth; height: @gHeight; position:absolute; top: @gPositionX; left:@gPositionY; z-index:@gZindex;">
                            <a href="@node.Url">
                                <img src="@graphic" width="@gWidth" height="@gHeight" alt="@planetTitle" title="@planetTitle" />                        
                            </a>
                        </div>

                    }
                    else
                    {
                       <div class="planet" style="width: @gWidth; height: @gHeight; position:absolute; top: @gPositionX; left:@gPositionY; z-index:@gZindex;">
                            <img src="@graphic" width="@gWidth" height="@gHeight" alt="@planetTitle" title="@planetTitle" />                        
                        </div>
                    }