Fixed memory leak if logging is done after SDL_Quit()

If someone calls SDL_Quit(), then runs an SDL function that implicitly initializes TLS or logging, and then calls SDL_Quit() again, we want to make sure we run through the quit process again. Each of the Init/Quit calls are protected against being called multiple times.

src/SDL_log.c

@@ -118,6 +118,7 @@ void SDL_InitLog(void)
 void SDL_QuitLog(void)
 {
     SDL_ResetLogPriorities();
+
     if (log_function_mutex) {
         SDL_DestroyMutex(log_function_mutex);
         log_function_mutex = NULL;