patch 8.1.2287: using EndOfBuffer highlight in popup does not look good

Problem:    Using EndOfBuffer highlight in popup does not look good.
Solution:   Do not EndOfBuffer highlight. (closes #5204)
diff --git a/src/drawscreen.c b/src/drawscreen.c
index abf34b5..2759257 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -2535,8 +2535,10 @@
 
 	// Make sure the rest of the screen is blank
 	// put '~'s on rows that aren't part of the file.
-	win_draw_end(wp, WIN_IS_POPUP(wp) ? ' ' : '~',
-				       ' ', FALSE, row, wp->w_height, HLF_EOB);
+	if (WIN_IS_POPUP(wp))
+	    win_draw_end(wp, ' ', ' ', FALSE, row, wp->w_height, HLF_AT);
+	else
+	    win_draw_end(wp, '~', ' ', FALSE, row, wp->w_height, HLF_EOB);
     }
 
 #ifdef SYN_TIME_LIMIT