elput: Fix issue of NULL seat named being passed during input init

When calling elput_input_init we need to check for a valid seat name
being passed in. If no seat name is provided, we will use the default
seat name.

@fix

Signed-off-by: Chris Michael <cpmichael@osg.samsung.com>

src/lib/elput/elput_input.c

@@ -226,6 +226,9 @@ elput_input_init(Elput_Manager *manager, const char *seat)
         goto udev_err;
      }
 
+   /* if not seat name is passed in, just use default seat name */
+   if (!seat) seat = "seat0";
+
    if (libinput_udev_assign_seat(manager->input.lib, seat) != 0)
      {
         ERR("libinput could not assign udev seat");