patch 8.0.0458: potential crash if adding list or dict to dict fails

Problem:    Potential crash if adding list or dict to dict fails.
Solution:   Make sure the reference count is correct. (Nikolai Pavlov, closes
            #1555)

Author: brammool

src/dict.c

@@ -356,12 +356,12 @@ dict_add_list(dict_T *d, char *key, list_T *list)
     item->di_tv.v_lock = 0;
     item->di_tv.v_type = VAR_LIST;
     item->di_tv.vval.v_list = list;
+    ++list->lv_refcount;
     if (dict_add(d, item) == FAIL)
     {
 	dictitem_free(item);
 	return FAIL;
     }
-    ++list->lv_refcount;
     return OK;
 }
 
@@ -380,12 +380,12 @@ dict_add_dict(dict_T *d, char *key, dict_T *dict)
     item->di_tv.v_lock = 0;
     item->di_tv.v_type = VAR_DICT;
     item->di_tv.vval.v_dict = dict;
+    ++dict->dv_refcount;
     if (dict_add(d, item) == FAIL)
     {
 	dictitem_free(item);
 	return FAIL;
     }
-    ++dict->dv_refcount;
     return OK;
 }
 

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    458,
 /**/
     457,
 /**/