vty: fix NULL-pointer dereference in cfg_bts_rep_dl_facch()

There is only one parameter in command:

  repeat dl-facch (command|all)

so indeed argv[0] must be used instead of argv[1].

Change-Id: I01efff109a33791e13b0149fc47c792d3266da71
Related: SYS#5114

src/osmo-bsc/bsc_vty.c

@@ -2760,7 +2760,7 @@ DEFUN_ATTR(cfg_bts_rep_dl_facch,
 		return CMD_WARNING;
 	}
 
-	if (!strcmp(argv[1], "command")) {
+	if (!strcmp(argv[0], "command")) {
 	        bts->repeated_acch_policy.dl_facch_cmd = true;
 	        bts->repeated_acch_policy.dl_facch_all = false;
 	} else {