Clear _focused_window in window destructor before calling OnFocuLost

This is such that EditBoxInGlobalFocus does not return true
within any OnFocusLost handlers

src/window.cpp

@@ -1092,8 +1092,8 @@ Window::~Window()
 
 	/* Make sure we don't try to access this window as the focused window when it doesn't exist anymore. */
 	if (_focused_window == this) {
-		this->OnFocusLost(nullptr);
 		_focused_window = nullptr;
+		this->OnFocusLost(nullptr);
 	}
 
 	this->DeleteChildWindows();