[DFU-UTIL][PATCH] fix some wrong option cause segment fault

[xiangfu]

Hi:

something like:
--------------------------
$ sudo ./dfu-util --d
dfu-util - (C) 2007 by OpenMoko Inc.
This program is Free Software and has ABSOLUTELY NO WARRANTY

Segmentation fault
--------------------------


Index: src/main.c
===================================================================
--- src/main.c	(revision 4878)
+++ src/main.c	(working copy)
@@ -408,6 +408,7 @@
 	{ "upload", 1, 0, 'U' },
 	{ "download", 1, 0, 'D' },
 	{ "reset", 0, 0, 'R' },
+	{ NULL, 0, NULL, 0 }
 };
 
 enum mode {