patch 7.4.2309

Problem:    Crash when doing tabnext in a BufUnload autocmd. (Dominique Pelle)
Solution:   When detecting that the tab page changed, don't just abort but
            delete the window where w_buffer is NULL.

src/version.c

@@ -763,6 +763,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2309,
 /**/
     2308,
 /**/