Revert "Fix incorrectly terminated MakeThreadHighPriority dbus message"

The first terminator is for input parameters. The second terminator was for the
output parameters.

If an error occurs when calling MakeThreadHighPriority(), e.g. a bad thread id,
then the reply from connection_send_with_reply_and_block() will be null.

src/core/linux/SDL_threadprio.c

@@ -68,7 +68,8 @@ rtkit_setpriority(pid_t thread, int nice_level)
 
     if (!dbus || !SDL_DBus_CallMethodOnConnection(dbus->system_conn,
             RTKIT_DBUS_NODE, RTKIT_DBUS_PATH, RTKIT_DBUS_INTERFACE, "MakeThreadHighPriority",
-            DBUS_TYPE_UINT64, &ui64, DBUS_TYPE_INT32, &si32, DBUS_TYPE_INVALID)) {
+            DBUS_TYPE_UINT64, &ui64, DBUS_TYPE_INT32, &si32, DBUS_TYPE_INVALID,
+            DBUS_TYPE_INVALID)) {
         return SDL_FALSE;
     }
     return SDL_TRUE;