Fix: IE9 throws an error when using document.activeElement in a frame

* See thread 21536 for more information

js/ext/ext.paging.js

@@ -142,17 +142,23 @@ $.extend( true, DataTable.ext.renderer, {
 				}
 			};
 
-			// Because this approach is destroying and recreating the paging
-			// elements, focus is lost on the select button which is bad for
-			// accessibility. So we want to restore focus once the draw has
-			// completed
-			var activeEl = $(document.activeElement).data('dt-idx');
-
-			attach( $(host).empty(), buttons );
-
-			if ( activeEl !== null ) {
-				$(host).find( '[data-dt-idx='+activeEl+']' ).focus();
+			// IE9 throws an 'unknown error' if document.activeElement is used
+			// inside an iframe or frame. Try / catch the error. Not good for
+			// accessibility, but neither are frames.
+			try {
+				// Because this approach is destroying and recreating the paging
+				// elements, focus is lost on the select button which is bad for
+				// accessibility. So we want to restore focus once the draw has
+				// completed
+				var activeEl = $(document.activeElement).data('dt-idx');
+
+				attach( $(host).empty(), buttons );
+
+				if ( activeEl !== null ) {
+					$(host).find( '[data-dt-idx='+activeEl+']' ).focus();
+				}
 			}
+			catch (e) {}
 		}
 	}
 } );