patch 8.0.0244: making t_BE empty only has an effect before startup

Problem:    When the user sets t_BE empty after startup to disable bracketed
            paste, this has no direct effect.
Solution:   When t_BE is made empty write t_BD.  When t_BE is made non-empty
            write the new value.
diff --git a/src/version.c b/src/version.c
index d86705f..e0f23d0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    244,
+/**/
     243,
 /**/
     242,