[gtk/wip/chergert/quartz4u] fix improper fallthrough

[Christian Hergert <chergert src gnome org>]

commit 7062aeaccdb42c25b6d66f17d150452f5fab53bc
Author: Christian Hergert <chergert redhat com>
Date:   Tue Apr 28 16:15:58 2020 -0700

    fix improper fallthrough

 gdk/macos/gdkmacossurface.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/gdk/macos/gdkmacossurface.c b/gdk/macos/gdkmacossurface.c
index e34c222ee2..b850191937 100644
--- a/gdk/macos/gdkmacossurface.c
+++ b/gdk/macos/gdkmacossurface.c
@@ -103,14 +103,18 @@ _gdk_macos_surface_new (GdkMacosDisplay   *display,
     {
     case GDK_SURFACE_TOPLEVEL:
       ret = _gdk_macos_toplevel_surface_new (display, parent, frame_clock, x, y, width, height);
+      break;
 
     case GDK_SURFACE_POPUP:
       ret = _gdk_macos_popup_surface_new (display, parent, frame_clock, x, y, width, height);
+      break;
 
     case GDK_SURFACE_TEMP:
       ret = _gdk_macos_drag_surface_new (display, parent, frame_clock, x, y, width, height);
+      break;
 
     default:
+      g_warn_if_reached ();
       ret = NULL;
     }