libnviz: Fix uninitialized warning and invalid pointer conversion

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@61046 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/nviz/draw.c

@@ -246,7 +246,7 @@ int Nviz_draw_all(nv_data * data)
     /* North Arrow */
     if (data->draw_arrow) {
 	gsd_north_arrow(data->arrow->where, data->arrow->size,
-			(GLuint)NULL, data->arrow->color, data->arrow->color);
+			0, data->arrow->color, data->arrow->color);
     }
 
     /* scale bar */

lib/nviz/map_obj.c

@@ -220,6 +220,8 @@ int Nviz_set_attr(int id, int type, int desc, int src,
 	    else if (src == MAP_ATT) {
 		ret = GS_load_att_map(id, str_value, desc);
 	    }
+	    else
+		ret = -1;
 
 	    /* After we've loaded a constant map or a file,
 	     * may need to adjust resolution if we are resetting