patch 8.1.0392: error while typing :/foo/s// with 'incsearch' enabled

Problem:    Error while typing :/foo/s// with 'incsearch' enabled.
Solution:   Do not give search errors when highlighting matches.
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index 79f8645..56e0bf2 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1055,6 +1055,10 @@
   call feedkeys(":/foo/s//\<Esc>", 'ntx')
   call assert_equal('bar', @/)
 
+  " no error message if pattern not found
+  call feedkeys(":/xyz/s//\<Esc>", 'ntx')
+  call assert_equal('bar', @/)
+
   bwipe!
   call test_override("ALL", 0)
   set noincsearch