vim-patch:9.1.0830: using wrong highlight group for spaces for popupmenu (#31054)

Problem:  using wrong highlight group for spaces for popupmenu
Solution: use original attribute instead of combined attributed
          (glepnir)

closes: vim/vim#15978

bc10be7a40

Co-authored-by: glepnir <glephunter@gmail.com>

test/functional/ui/popupmenu_spec.lua

@@ -5190,10 +5190,18 @@ describe('builtin popupmenu', function()
       -- oldtest: Test_pum_user_abbr_hlgroup()
       it('custom abbr_hlgroup override', function()
         exec([[
-          func CompleteFunc( findstart, base )
+          let s:var = 0
+          func CompleteFunc(findstart, base)
             if a:findstart
               return 0
             endif
+            if s:var == 1
+              return {
+                    \ 'words': [
+                    \ { 'word': 'aword1', 'abbr_hlgroup': 'StrikeFake' },
+                    \ { 'word': '你好', 'abbr_hlgroup': 'StrikeFake' },
+                    \]}
+            endif
             return {
                   \ 'words': [
                   \ { 'word': 'aword1', 'menu': 'extra text 1', 'kind': 'W', 'abbr_hlgroup': 'StrikeFake' },
@@ -5201,6 +5209,9 @@ describe('builtin popupmenu', function()
                   \ { 'word': '你好', 'menu': 'extra text 3', 'kind': 'W', 'abbr_hlgroup': 'StrikeFake' },
                   \]}
           endfunc
+          func ChangeVar()
+            let s:var = 1
+          endfunc
           set completeopt=menu
           set completefunc=CompleteFunc
 
@@ -5243,6 +5254,17 @@ describe('builtin popupmenu', function()
           {2:-- }{5:match 2 of 3}                 |
         ]])
         feed('<C-E><Esc>')
+
+        command('call ChangeVar()')
+        feed('S<C-X><C-U>')
+        screen:expect([[
+          aword1^                          |
+          {ds:aword1}{s:         }{1:                 }|
+          {dn:你好}{n:           }{1:                 }|
+          {1:~                               }|*16
+          {2:-- }{5:match 1 of 2}                 |
+        ]])
+        feed('<C-E><Esc>')
       end)
 
       -- oldtest: Test_pum_user_kind_hlgroup()