Assert that typelib_typedescription_release will not destroy pTDR->pType

...which is dereferenced a few lines further down; this is in preparation for a
commit addressing cid#440589.

Change-Id: I3428216258d928473f85ecd4d025c352c8c83ea0

cppu/source/typelib/typelib.cxx

@@ -1556,6 +1556,7 @@ extern "C" CPPU_DLLPUBLIC void SAL_CALL typelib_typedescription_register(
                 else if( !pTDR->pType->bOnDemand && (*ppNewDescription)->bOnDemand )
                 {
                     // switch from !OnDemand to OnDemand, so the description must be relesed
+                    assert(pTDR->pType->nRefCount > 1);
                     typelib_typedescription_release( pTDR->pType );
                 }