patch 8.1.1390: search stats are off when using count or offset

Problem:    Search stats are off when using count or offset.
Solution:   Recompute the stats when needed. (Masato Nishihata, closes #4410)
diff --git a/src/testdir/test_search_stat.vim b/src/testdir/test_search_stat.vim
index ad46b2d..cf36f32 100644
--- a/src/testdir/test_search_stat.vim
+++ b/src/testdir/test_search_stat.vim
@@ -117,6 +117,25 @@
     call assert_false(1)
   endtry
 
+  " with count
+  call cursor(1, 1)
+  let @/ = 'fo*\(bar\?\)\?'
+  let g:a = execute(':unsilent :norm! 2n')
+  let stat = '\[3/50\]'
+  let pat = escape(@/, '()*?'). '\s\+'
+  call assert_match(pat .. stat, g:a)
+  let g:a = execute(':unsilent :norm! 2n')
+  let stat = '\[5/50\]'
+  call assert_match(pat .. stat, g:a)
+
+  " with offset
+  call cursor(1, 1)
+  call feedkeys("/fo*\\(bar\\?\\)\\?/+1\<cr>", 'tx')
+  let g:a = execute(':unsilent :norm! n')
+  let stat = '\[5/50\]'
+  let pat = escape(@/ .. '/+1', '()*?'). '\s\+'
+  call assert_match(pat .. stat, g:a)
+
   " normal, n comes from a mapping
   "     Need to move over more than 64 lines to trigger char_avail(.
   nnoremap n nzv