patch 8.1.0746: highlighting not updated with conceal and 'cursorline'

Problem:    Highlighting not updated with conceal and 'cursorline'. (Jason
            Franklin)
Solution:   Do not use a zero line number.  Check if 'conceallevel' is set for
            the current window.
diff --git a/src/testdir/test_conceal.vim b/src/testdir/test_conceal.vim
index 4a053875..685c891 100644
--- a/src/testdir/test_conceal.vim
+++ b/src/testdir/test_conceal.vim
@@ -109,3 +109,28 @@
   call StopVimInTerminal(buf)
   call delete('XTest_conceal')
 endfunc
+
+func Test_conceal_with_cursorline()
+  " Opens a help window, where 'conceal' is set, switches to the other window
+  " where 'cursorline' needs to be updated when the cursor moves.
+  call writefile([
+	\ 'set cursorline',
+	\ 'normal othis is a test',
+	\ 'new',
+	\ 'call setline(1, ["one", "two", "three", "four", "five"])',
+	\ 'set ft=help',
+	\ 'normal M',
+	\ ], 'XTest_conceal_cul')
+  let buf = RunVimInTerminal('-S XTest_conceal_cul', {})
+  call VerifyScreenDump(buf, 'Test_conceal_cul_01', {})
+
+  call term_sendkeys(buf, ":wincmd w\r")
+  call VerifyScreenDump(buf, 'Test_conceal_cul_02', {})
+
+  call term_sendkeys(buf, "k")
+  call VerifyScreenDump(buf, 'Test_conceal_cul_03', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XTest_conceal_cul')
+endfunc