Set the progress message in showWhile only if different than null
diff --git a/bundles/org.eclipse.orion.client.core/web/orion/progress.js b/bundles/org.eclipse.orion.client.core/web/orion/progress.js
index ed82dd6..2b27e1e 100644
--- a/bundles/org.eclipse.orion.client.core/web/orion/progress.js
+++ b/bundles/org.eclipse.orion.client.core/web/orion/progress.js
@@ -237,7 +237,8 @@
 			 * @returns

 			 */

 			showWhile: function(deferred, message){

-				this._serviceRegistry.getService("orion.page.message").setProgressMessage(message);

+				if(message)

+					this._serviceRegistry.getService("orion.page.message").setProgressMessage(message);

 				var that = this;

 				return deferred.then(function(jsonResult){

 					//see if we are dealing with a progress resource