Fix another memory leak found by scan-build (in an error condition).

src/sbbs3/scfg/scfgmsg.c

@@ -132,6 +132,7 @@ static bool new_grp(unsigned new_grpnum)
 
 	grp_t** new_grp_list;
 	if ((new_grp_list = (grp_t **)realloc(cfg.grp, sizeof(grp_t *)*(cfg.total_grps + 1))) == NULL) {
+		free(new_group);
 		errormsg(WHERE, ERR_ALLOC, "group list", cfg.total_grps + 1);
 		return false;
 	}