Fix CreateApplicationShortcutView::AddCheckbox compile error

It was failing to compile on Win-Clang with this error message:

..\..\chrome\browser\ui\views\create_application_shortcut_view.cc(397,79) :
error: non-pointer operand type 'bool' incompatible with nullptr
  creation_locations.in_quick_launch_bar = quick_launch_check_box_ == nullptr ?
                                                                              ^

TBR=bcwhite, msw
BUG=82385

Review URL: https://codereview.chromium.org/1372623003

Cr-Commit-Position: refs/heads/master@{#350846}
1 file changed