Don't crash if a manager connection provides a username that exists in

manager.conf but does not have a password, and also requests MD5 
authentication. (ASA-2007-012)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.2@61786 65c4cc65-6c06-0410-ace0-fbb531ad65f3

manager.c

@@ -533,7 +533,8 @@ static int authenticate(struct mansession *s, struct message *m)
 				} else if (ha)
 					ast_free_ha(ha);
 				if (!strcasecmp(authtype, "MD5")) {
-					if (!ast_strlen_zero(key) && s->challenge) {
+					if (!ast_strlen_zero(key) && 
+					    !ast_strlen_zero(s->challenge) && !ast_strlen_zero(password)) {
 						int x;
 						int len=0;
 						char md5key[256] = "";