updated for version 7.4.645
Problem:    When splitting the window in a BufAdd autocommand while still in
            the first, empty buffer the window count is wrong.
Solution:   Do not reset b_nwindows to zero and don't increment it.
diff --git a/src/version.c b/src/version.c
index 38f3b78..41926a4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    645,
+/**/
     644,
 /**/
     643,