Insert a Signature Line, right click, Sign..., Cancel

include/vcl/vclptr.hxx:116: VclPtr<T>::~VclPtr() [with reference_type = AbstractSignSignatureLineDialog]: Assertion `(!m_rInnerRef.get() || m_rInnerRef->isDisposed() || m_rInnerRef->getRefCount() > 1) && "someone forgot to call dispose()"' failed.

Change-Id: I09a1b37b917b267a84ee95fb375658974ee1b320
Reviewed-on: https://gerrit.libreoffice.org/57913
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>