composer: Fix TUI state during unprepare

Change-Id: Ib326836196e22ba9fb4264c05e4ec236081713b0
diff --git a/composer/hwc_display.cpp b/composer/hwc_display.cpp
index a2a73d4..b35a41e 100755
--- a/composer/hwc_display.cpp
+++ b/composer/hwc_display.cpp
@@ -3093,7 +3093,11 @@
   }
 
   if (update_event_only) {
-    secure_event_ = secure_event;
+    if (secure_event == kTUITransitionPrepare) {
+      secure_event_ = kTUITransitionPrepare;
+    } else {
+      secure_event_ = kSecureEventMax;
+    }
     return kErrorNone;
   }