If there are no completions matching, detach the completer.

This prevents an invisible completer from swallowing keystrokes such as up/down

services/web/public/coffee/ide/editor/directives/aceEditor/auto-complete/AutoCompleteManager.coffee

@@ -134,6 +134,8 @@ define [
 						editor.completer.showPopup(editor)
 						editor.completer.cancelContextMenu()
 						$(editor.completer.popup?.container).css({'font-size': @$scope.fontSize + 'px'})
+						if editor.completer?.completions?.filtered?.length == 0
+							editor.completer.detach()
 					bindKey: "Ctrl-Space|Ctrl-Shift-Space|Alt-Space"
 				}