exit () on JavaScript exceptions

This is better than being in a wedged state.  See the comment
for more argument.

src/gnome-shell-plugin.c

@@ -202,8 +202,20 @@ gnome_shell_plugin_constructed (GObject *object)
                          &status,
                          &error))
     {
-      g_warning ("Evaling main.js failed: %s", error->message);
+      g_message ("Execution of main.js threw exception: %s", error->message);
       g_error_free (error);
+      /* We just exit() here, since in a development environment you'll get the
+       * error in your shell output, and it's way better than a busted WM,
+       * which typically manifests as a white screen.
+       *
+       * In production, we shouldn't crash =)  But if we do, we should get
+       * restarted by the session infrastructure, which is likely going
+       * to be better than some undefined state.
+       *
+       * If there was a generic "hook into bug-buddy for non-C crashes"
+       * infrastructure, here would be the place to put it.
+       */
+      exit (1);
     }
 }