Backport of r62669 to 2.8 branch. Fix crash when dragging toolbars in wxAuiManager::OnFloatingPaneMoveStart(). (fixes #10170)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@62670 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/aui/framemanager.cpp

@@ -3443,6 +3443,9 @@ void wxAuiManager::OnFloatingPaneMoveStart(wxWindow* wnd)
     wxAuiPaneInfo& pane = GetPane(wnd);
     wxASSERT_MSG(pane.IsOk(), wxT("Pane window not found"));
 
+    if(!pane.frame)
+        return;
+
     if (m_flags & wxAUI_MGR_TRANSPARENT_DRAG)
         pane.frame->SetTransparent(150);
 }