patch 8.1.0876: completion match not displayed when popup menu is not shown

Problem:    Completion match not displayed when popup menu is not shown.
Solution:   Call update_screen() when not displaying the popup menu to show
            the inserted match. (Ken Takata, Hirohito Higashi)

src/edit.c

@@ -5021,9 +5021,13 @@ ins_compl_next(
 	/* may undisplay the popup menu first */
 	ins_compl_upd_pum();
 
-	// Redraw before showing the popup menu to show the user what was
-	// inserted.
+	if (pum_enough_matches())
+	    // Will display the popup menu, don't redraw yet to avoid flicker.
 	    pum_call_update_screen();
+	else
+	    // Not showing the popup menu yet, redraw to show the user what was
+	    // inserted.
+	    update_screen(0);
 
 	/* display the updated popup menu */
 	ins_compl_show_pum();

src/version.c

@@ -783,6 +783,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    876,
 /**/
     875,
 /**/