patch 8.1.1108: test for 'visualbell' doesn't work

Problem:    Test for 'visualbell' doesn't work.
Solution:   Make 'belloff' empty.
diff --git a/src/version.c b/src/version.c
index e1809c6..08493fe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1108,
+/**/
     1107,
 /**/
     1106,