Initialize m_containsFullscreenElement

Author: peiche-ms

WebView2APISample/AppWindow.h

@@ -103,7 +103,7 @@ class AppWindow
     // Fullscreen related code
     WINDOWPLACEMENT m_previousPlacement;
     HMENU m_hMenu;
-    BOOL m_containsFullscreenElement;
+    BOOL m_containsFullscreenElement = TRUE;
     bool m_fullScreenAllowed = true;
     void EnterFullScreen();
     void ExitFullScreen();