Various bugfixes

bootloader/libs/fatfs/ff.c

@@ -4726,7 +4726,7 @@ FRESULT f_getfree (
 	/* Get logical drive */
 	res = find_volume(&path, &fs, 0);
 	if (res == FR_OK) {
-		*fatfs = fs;				/* Return ptr to the fs object */
+		if (fatfs) *fatfs = fs;	/* Return ptr to the fs object */
 		/* If free_clst is valid, return it without full FAT scan */
 		if (fs->free_clst <= fs->n_fatent - 2) {
 			*nclst = fs->free_clst;