grdview: Fix the bug for the default z-plane when only -N is set (#8838)

Author: seisman

src/grdview.c

@@ -608,9 +608,9 @@ static int parse (struct GMT_CTRL *GMT, struct GRDVIEW_CTRL *Ctrl, struct GMT_OP
 					n_errors += gmt_default_option_error (GMT, opt);
 				break;
 			case 'N':	/* Facade */
+				n_errors += gmt_M_repeated_module_option (API, Ctrl->N.active);
 				if (opt->arg[0]) {
 					char colors[GMT_LEN64] = {""};
-					n_errors += gmt_M_repeated_module_option (API, Ctrl->N.active);
 					if ((c = strstr (opt->arg, "+g")) != NULL) {	/* Gave modifier +g<fill> */
 						c[0] = '\0';	/* Truncate string temporarily */
 						if (opt->arg[0])