[four-in-a-row] Improve keyboard handling on gameover.

[Arnaud B. <arnaudb src gnome org>]

commit bb98800a7007e23a92942975bb07509acd25612d
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Sun Dec 22 22:43:14 2019 +0100

    Improve keyboard handling on gameover.

 src/four-in-a-row.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/four-in-a-row.vala b/src/four-in-a-row.vala
index bd532cb..0ab2245 100644
--- a/src/four-in-a-row.vala
+++ b/src/four-in-a-row.vala
@@ -875,7 +875,7 @@ private class FourInARow : Gtk.Application
             return false;
 
         string key = (!) (Gdk.keyval_name (event.keyval) ?? "");
-        if (key == "" || key == "Tab")
+        if (key == "" || key == "Tab" || event.is_modifier == 1)
             return false;
 
         if (gameover)