Fixes crash of compositor when unvalidated keycode 0 is passed (#1833)

* Fixes crash of compositor when unvalidated keycode 0 is passed from virtual keyboard

* Style fix

types/wlr_virtual_keyboard_v1.c

@@ -75,6 +75,9 @@ context_fail:
 static void virtual_keyboard_key(struct wl_client *client,
 		struct wl_resource *resource, uint32_t time, uint32_t key,
 		uint32_t state) {
+	if (key == 0) {
+		return;
+	}
 	struct wlr_virtual_keyboard_v1 *keyboard =
 		virtual_keyboard_from_resource(resource);
 	if (!keyboard->has_keymap) {