Stop timers, and guard against emission on disposed navigator.

Change-Id: Ide1f94c07c83a5b8d9a522e02177ad2fe481eff2
diff --git a/sw/source/uibase/utlui/navipi.cxx b/sw/source/uibase/utlui/navipi.cxx
index f5f788f..ed513a5 100644
--- a/sw/source/uibase/utlui/navipi.cxx
+++ b/sw/source/uibase/utlui/navipi.cxx
@@ -878,6 +878,9 @@ void SwNavigationPI::dispose()
    aContentTree.disposeAndClear();
    aGlobalTree.disposeAndClear();
    aDocListBox.disposeAndClear();

    aPageChgIdle.Stop();

    vcl::Window::dispose();
}

@@ -1249,8 +1252,11 @@ bool    SwNavigationPI::IsGlobalDoc() const

IMPL_LINK_NOARG(SwNavigationPI, ChangePageHdl)
{
    EditAction(&GetPageEdit());
    GetPageEdit().GrabFocus();
    if (!IsDisposed())
    {
        EditAction(&GetPageEdit());
        GetPageEdit().GrabFocus();
    }
    return 0;
}