patch 8.2.5151: reading beyond the end of the line with lisp indenting

Problem:    Reading beyond the end of the line with lisp indenting.
Solution:   Avoid going over the NUL at the end of the line.
diff --git a/src/testdir/test_lispwords.vim b/src/testdir/test_lispwords.vim
index ff710b2..4144fb0 100644
--- a/src/testdir/test_lispwords.vim
+++ b/src/testdir/test_lispwords.vim
@@ -1,4 +1,5 @@
-" Tests for 'lispwords' settings being global-local
+" Tests for 'lispwords' settings being global-local.
+" And  other lisp indent stuff.
 
 set nocompatible viminfo+=nviminfo
 
@@ -85,4 +86,13 @@
   set nolisp
 endfunc
 
+func Test_lisp_indent_works()
+  " This was reading beyond the end of the line
+  new
+  exe "norm a\tü(\<CR>="
+  set lisp
+  norm ==
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab