updated for version 7.3.893
Problem:    Crash when using b:, w: or t: after closing the buffer, window or
            tabpage.
Solution:   Allocate the dictionary instead of having it part of the
            buffer/window/tabpage struct. (Yukihiro Nakadaira)
diff --git a/src/fileio.c b/src/fileio.c
index 6e89b88..251d155 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -8955,8 +8955,8 @@
 	    /* Hmm, original window disappeared.  Just use the first one. */
 	    curwin = firstwin;
 # ifdef FEAT_EVAL
-	vars_clear(&aucmd_win->w_vars.dv_hashtab);  /* free all w: variables */
-	hash_init(&aucmd_win->w_vars.dv_hashtab);   /* re-use the hashtab */
+	vars_clear(&aucmd_win->w_vars->dv_hashtab);  /* free all w: variables */
+	hash_init(&aucmd_win->w_vars->dv_hashtab);   /* re-use the hashtab */
 # endif
 #else
 	curwin = aco->save_curwin;