patch 9.1.0830: using wrong highlight group for spaces for popupmenu

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

closes: #15978

Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/popupmenu.c b/src/popupmenu.c
index 4d77c66..be8016f 100644
--- a/src/popupmenu.c
+++ b/src/popupmenu.c
@@ -839,11 +839,11 @@
 #ifdef FEAT_RIGHTLEFT
 	if (pum_rl)
 	    screen_fill(row, row + 1, pum_col - pum_width + 1, col + 1, ' ',
-								    ' ', attr);
+								    ' ', orig_attr);
 	else
 #endif
 	    screen_fill(row, row + 1, col, pum_col + pum_width, ' ', ' ',
-									attr);
+									orig_attr);
 	if (pum_scrollbar > 0)
 	{
 #ifdef FEAT_RIGHTLEFT