Fixed small issues with present module:

- disable the close button on the window
- thumbnails no longer throw exception if clicked when empty

git-svn-id: http://bigbluebutton.googlecode.com/svn/trunk@3090 af16638f-c34d-0410-8cfa-b39d5352b314

bigbluebutton-client/src/org/bigbluebutton/modules/present/views/FisheyeThumbnail.mxml

@@ -71,6 +71,7 @@
 			}
 			
 			public function selectSlide():void{
+				if (images == null) return;
 				dispatchEvent(new PresenterCommands(PresenterCommands.GOTO_SLIDE, fisheye.selectedIndex));
 			}
 			

bigbluebutton-client/src/org/bigbluebutton/modules/present/views/PresentationWindow.mxml

@@ -26,6 +26,7 @@
 	xmlns:pres="flexlib.mdi.containers.*"
 	paddingBottom="0" paddingTop="0" 
 	paddingLeft="0" paddingRight="0" 
+	showCloseButton="false"
     verticalScrollPolicy="off" horizontalScrollPolicy="off"
 	implements="org.bigbluebutton.common.IBbbModuleWindow"
 	mouseMove="thumbnailDisplay()"