allow recovery UI to ignore certain keypresses

Change-Id: Id182bb95ffcc475c5acabb29b413e422302ae7f2
diff --git a/ui.cpp b/ui.cpp
index fd370a7..bd0fcae 100644
--- a/ui.cpp
+++ b/ui.cpp
@@ -123,6 +123,9 @@
 
     if (register_key) {
         switch (CheckKey(key_code)) {
+          case RecoveryUI::IGNORE:
+            break;
+
           case RecoveryUI::TOGGLE:
             ShowText(!IsTextVisible());
             break;