patch 8.2.1580: wildmenu does not work properly

Problem:    Wildmenu does not work properly.
Solution:   Do not call may_do_incsearch_highlighting() if completion is in
            progress.
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 266513e..6ebfa31 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -84,6 +84,34 @@
   call delete('Xdir1', 'd')
   set nowildmenu
 endfunc
+f
+func Test_wildmenu_screendump()
+  CheckScreendump
+
+  let lines =<< trim [SCRIPT]
+    set wildmenu hlsearch
+  [SCRIPT]
+  call writefile(lines, 'XTest_wildmenu')
+
+  let buf = RunVimInTerminal('-S XTest_wildmenu', {'rows': 8})
+  call term_sendkeys(buf, ":vim\<Tab>")
+  call VerifyScreenDump(buf, 'Test_wildmenu_1', {})
+
+  call term_sendkeys(buf, "\<Tab>")
+  call VerifyScreenDump(buf, 'Test_wildmenu_2', {})
+
+  call term_sendkeys(buf, "\<Tab>")
+  call VerifyScreenDump(buf, 'Test_wildmenu_3', {})
+
+  call term_sendkeys(buf, "\<Tab>")
+  call VerifyScreenDump(buf, 'Test_wildmenu_4', {})
+  call term_sendkeys(buf, "\<Esc>")
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XTest_wildmenu')
+endfunc
+
 
 func Test_map_completion()
   CheckFeature cmdline_compl