patch 8.1.0567: error for NUL byte in ScreenLines goes unnoticed

Problem:    Error for NUL byte in ScreenLines goes unnoticed.
Solution:   Add an internal error message.
diff --git a/src/version.c b/src/version.c
index b912a6e..c4d9a8f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -793,6 +793,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    567,
+/**/
     566,
 /**/
     565,