patch 9.0.1864: still crash with bt_quickfix1_poc

Problem:  crash with bt_quickfix1_poc when cleaning up
          and EXITFREE is defined
Solution: Test if buffer is valid in a window, else close
          window directly, don't try to access buffer properties

While at it, increase the crash timeout slightly, so that CI has a
chance to finish processing the test_crash() test.

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1864,
 /**/
     1863,
 /**/