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)
diff --git a/src/dict.c b/src/dict.c
index 7074305..a26419b 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -356,12 +356,12 @@
     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 @@
     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;
 }
 
diff --git a/src/version.c b/src/version.c
index 81ef80f..2e21198 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    458,
+/**/
     457,
 /**/
     456,