updated for version 7.3.005

Problem:    Crash when using undotree(). (Christian Brabandt)
Solution:   Increase the list reference count.  Add a test for undotree()
            (Lech Lorens)

src/eval.c

@@ -7075,7 +7075,7 @@ dict_add_nr_str(d, key, nr, str)
 }
 
 /*
- * Add a list  entry to dictionary "d".
+ * Add a list entry to dictionary "d".
  * Returns FAIL when out of memory and when key already exists.
  */
     int
@@ -7097,6 +7097,7 @@ dict_add_list(d, key, list)
 	dictitem_free(item);
 	return FAIL;
     }
+    ++list->lv_refcount;
     return OK;
 }