Don't quit debugger when the program terminates, only after `quit`.

tests/debugger/empty_column_test.dart

 // Copyright (c) 2015, the Dartino project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 // Test that we get a meaningful breakpoint when breaking on a whitespace
 // column.
 
-// DartinoDebuggerCommands=bf tests/debugger/empty_column_test.dart 12 1,r,c
+// DartinoDebuggerCommands=bf tests/debugger/empty_column_test.dart 12 1,r,c,q
 
 int foo() {
   int x = 2;
   int y = 3; // break here.
   return x + y;
 }
 
 main() {
   return foo() - 5;
 }