Bug fix as reported by Fish-Face/Chris Le Sueur on IRC

After deleting an object, the call free_and_unlink_base() takes care of
NULLifying object pointers. But, with exception of constraints. Silly!!!

So, in the end of a function additionally the test_scene_constraints()
has to be called to prevent crashes. This was missing in join_mesh and
convert_object.

source/blender/src/editobject.c

@@ -248,6 +248,7 @@ void add_objectLamp(short type)
 	allqueue(REDRAWALL, 0);
 }
 
+// really bad, doesnt do constraints, that has been coded in test_scene_constraints();
 void free_and_unlink_base(Base *base)
 {
 	if (base==BASACT)
@@ -287,7 +288,8 @@ void delete_obj(int ok)
 	
 	if(islamp && G.vd->drawtype==OB_SHADED) reshadeall_displist();
 
-	test_scene_constraints();
+	test_scene_constraints(); // do because of delete obj
+	
 	allqueue(REDRAWVIEW3D, 0);
 	redraw_test_buttons(OBACT);
 	allqueue (REDRAWACTION, 0);
@@ -2272,6 +2274,9 @@ void convertmenu(void)
 			free_and_unlink_base(basedel);	
 		basedel = NULL;				
 	}
+	
+	test_scene_constraints();	// always call after delete object
+	
 	countall();
 	allqueue(REDRAWVIEW3D, 0);
 	allqueue(REDRAWOOPS, 0);

source/blender/src/meshtools.c

@@ -432,6 +432,8 @@ void join_mesh(void)
 	enter_editmode();
 	exit_editmode(1);	// freedata, but no undo
 	
+	test_scene_constraints(); // always call after delete object (stupid!)
+
 	allqueue(REDRAWVIEW3D, 0);
 	allqueue(REDRAWBUTSSHADING, 0);
 	makeDispList(ob);