Always show uploaded presentation if no presentation is active yet.

static/js/directives/presentation.js

@@ -518,8 +518,8 @@ define(['jquery', 'underscore', 'text!partials/presentation.html', 'bigscreen'],
 					});
 				});
 				var presentation = uploadPresentation(file);
-				if ($scope.availablePresentations.length === 1) {
+				if (!$scope.currentPresentation) {
-					// this is the first presentation, show immediately
+					// no presentation active, show immediately
 					$scope.selectPresentation(presentation);
 				}
 			};