patch 8.0.0177: BufEnter autocommand not fired for a directory

Problem:    When opening a buffer on a directory and inside a try/catch then
            the BufEnter event is not triggered.
Solution:   Return NOTDONE from readfile() for a directory and deal with the
            three possible return values. (Justin M. Keyes, closes #1375,
            closes #1353)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 134a488..295e539 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -8857,7 +8857,7 @@
 			  eap->line2, (linenr_T)0, (linenr_T)MAXLNUM, eap, 0);
 
 	}
-	if (i == FAIL)
+	if (i != OK)
 	{
 #if defined(FEAT_AUTOCMD) && defined(FEAT_EVAL)
 	    if (!aborting())