Fix a bug in dummyflasher.c special case where no type parameter is given

Corresponding to flashrom svn r577.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>

dummyflasher.c

@@ -35,7 +35,7 @@ int dummy_init(void)
 	printf_debug("%s\n", __func__);
 
 	/* "all" is equivalent to specifying no type. */
-	if (!strcmp(dummytype, "all")) {
+	if (dummytype && (!strcmp(dummytype, "all"))) {
 		free(dummytype);
 		dummytype = NULL;
 	}