Update GridView.xml (#1947)

* Update GridView.xml

* Update xml/System.Web.UI.WebControls/GridView.xml

Just a syntax change? Yes, of course that is good.

Co-Authored-By: SimpleSamples <[email protected]>

Author: SimpleSamples

xml/System.Web.UI.WebControls/GridView.xml

@@ -5872,7 +5872,7 @@
       </ReturnValue>
       <Docs>
         <summary>Gets a reference to a <see cref="T:System.Web.UI.WebControls.GridViewRow" /> object that represents the selected row in the control.</summary>
-        <value>A <see cref="T:System.Web.UI.WebControls.GridViewRow" /> that represents the selected row in the control.</value>
+        <value>A <see cref="T:System.Web.UI.WebControls.GridViewRow" /> that represents the selected row in the control, or `null` if nothing is selected.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
@@ -7647,4 +7647,4 @@
       </Docs>
     </Member>
   </Members>
-</Type>
+</Type>