app_server: Remove window token first in ~ServerWindow.

This way, if the Desktop has locked its window list, RemoveWindow
will wait until the lock is released, at which time we're guaranteed
that the Desktop object will no longer be using this window.

May fix #19750 and related tickets.

src/servers/app/ServerWindow.cpp

@@ -202,9 +202,12 @@ ServerWindow::~ServerWindow()
 {
 	STRACE(("ServerWindow(%s@%p):~ServerWindow()\n", fTitle, this));
 
+	BPrivate::gDefaultTokens.RemoveToken(fServerToken);
+
 	if (!fWindow->IsOffscreenWindow()) {
 		fWindowAddedToDesktop = false;
 		fDesktop->RemoveWindow(fWindow.Get());
+		fDesktop = NULL;
 	}
 
 	if (App() != NULL) {
@@ -217,8 +220,6 @@ ServerWindow::~ServerWindow()
 	free(fTitle);
 	delete_port(fMessagePort);
 
-	BPrivate::gDefaultTokens.RemoveToken(fServerToken);
-
 	fDirectWindowInfo.Unset(); // TODO: is it really needed?
 	STRACE(("ServerWindow(%p) will exit NOW\n", this));