Index: dimension.c
===================================================================
--- dimension.c	(revision 28785)
+++ dimension.c	(revision 28786)
@@ -37,6 +37,13 @@
 	double x1, y1, x2, y2, len, dx, dy;
 } dimension;
 
+static void pcb_dimension_del_pre(pcb_subc_t *subc)
+{
+	pcb_trace("dim del_pre\n");
+	free(subc->extobj_data);
+	subc->extobj_data = NULL;
+}
+
 static int dimension_update_src(dimension *dim, pcb_any_obj_t *edit)
 {
 	dim->valid = 0;
@@ -287,6 +294,8 @@
 pcb_trace("let's do it!\n");
 
 	edit_obj = pcb_extobj_get_editobj_by_attr(subc);
+	if (edit_obj == NULL)
+		return;
 	dimension_clear(subc);
 	dim->displace = d;
 	dimension_gen(subc, edit_obj);
@@ -311,5 +320,6 @@
 	pcb_dimension_edit_geo,
 	pcb_dimension_float_pre,
 	pcb_dimension_float_geo,
-	pcb_dimension_chg_attr
+	pcb_dimension_chg_attr,
+	pcb_dimension_del_pre
 };
Index: line_of_vias.c
===================================================================
--- line_of_vias.c	(revision 28785)
+++ line_of_vias.c	(revision 28786)
@@ -35,6 +35,13 @@
 	double len, dx, dy;
 } line_of_vias;
 
+static void pcb_line_of_vias_del_pre(pcb_subc_t *subc)
+{
+	pcb_trace("LoV del_pre\n");
+	free(subc->extobj_data);
+	subc->extobj_data = NULL;
+}
+
 static void line_of_vias_udpate_line(line_of_vias *lov, pcb_line_t *line)
 {
 	lov->x1 = line->Point1.X;
@@ -184,6 +191,8 @@
 	pcb_trace("LoV chg_attr\n");
 	if (strncmp(key, "extobj::", 8) == 0) {
 		pcb_any_obj_t *edit_obj = pcb_extobj_get_editobj_by_attr(subc);
+		if (edit_obj == NULL)
+			return;
 		line_of_vias_clear(subc);
 		line_of_vias_unpack(subc);
 		line_of_vias_gen(subc, edit_obj);
@@ -199,5 +208,6 @@
 	pcb_line_of_vias_edit_geo,
 	NULL, /* float_pre */
 	NULL, /* float_geo */
-	pcb_line_of_vias_chg_attr
+	pcb_line_of_vias_chg_attr,
+	pcb_line_of_vias_del_pre
 };