patch 8.0.0340: not checking return valud of dict_add()

Problem:    Not checking return valud of dict_add(). (Coverity)
Solution:   Handle a failure.

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    340,
 /**/
     339,
 /**/