keyboard: Re-apply modifiers masks

Restore modifiers masks removed by mistake in previous commit.

Signed-off-by: Olivier Fourdan <fourdan@xfce.org>

src/keyboard.c

@@ -110,6 +110,8 @@ getModifierMap (const char *str, guint *map)
         ret &= addModifierMap (map, MetaMask);
     }
 
+    *map &= MODIFIER_MASK & ~IGNORE_MASK;
+
     return ret;
 }