patch 8.1.1264: crash when closing window from WinBar click

Problem:    Crash when closing window from WinBar click. (Ben Jackson)
Solution:   Check that window pointer is still valid. (closes #4337)
diff --git a/src/version.c b/src/version.c
index f5faef3..f2abf24 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1264,
+/**/
     1263,
 /**/
     1262,