we can be in shutdown state, which means keys can be destroyed

ChangeLog

@@ -1,6 +1,8 @@
  (Format: Year/Month/Day)
 Changes for 1.0.1:
 *07/10/22:
+   * Fixed crash bug at restart. ( Henrik )
+     Window.cc
    * Replaced modKey with new commands StartMoving and StartResizing (Mark)
      - your keys file should be updated automatically
      - they must be used with a mouse button, or they won't work

src/Window.cc

@@ -295,8 +295,11 @@ FluxboxWindow::FluxboxWindow(WinClient &client, FbWinFrameTheme &tm,
 FluxboxWindow::~FluxboxWindow() {
     if (WindowCmd<void>::window() == this)
         WindowCmd<void>::setWindow(0);
+    if ( Fluxbox::instance()->keys() != 0 ) {
+        Fluxbox::instance()->keys()->
+            unregisterWindow(frame().window().window());
+    }
 
-    Fluxbox::instance()->keys()->unregisterWindow(frame().window().window());
 
 #ifdef DEBUG
     const char* title = m_client ? m_client->title().c_str() : "" ;