Crash in Qt Assistant

Introduced by 9a5fb6bd5f0fb3b37897bf722e4cc1673309623c (SQLite fix).

Exit crash on Linux, Crash on startup on Windows.

0 ?? 0 0x50
1 QMetaObject::cast qmetaobject.cpp 292 0x7ffff3ec6d14
2 qobject_cast<QSQLiteDriver const*> qobject.h 389 0x7fffed4f841e
3 QSQLiteResult::~QSQLiteResult qsql_sqlite.cpp 295 0x7fffed4f486f
4 QSQLiteResult::~QSQLiteResult qsql_sqlite.cpp 298 0x7fffed4f4912
5 QSqlQueryPrivate::~QSqlQueryPrivate qsqlquery.cpp 94 0x7ffff565584a
6 QSqlQuery::~QSqlQuery qsqlquery.cpp 245 0x7ffff56558d9
7 QHelpCollectionHandler::~QHelpCollectionHandler qhelpcollectionhandler.cpp 68 0x7ffff7b7ebff
8 QHelpCollectionHandler::~QHelpCollectionHandler qhelpcollectionhandler.cpp 73 0x7ffff7b7ecbe
9 QHelpEngineCorePrivate::~QHelpEngineCorePrivate qhelpenginecore.cpp 76 0x7ffff7b53331
10 QHelpEngineCorePrivate::~QHelpEngineCorePrivate qhelpenginecore.cpp 78 0x7ffff7b53482
11 QHelpEngineCore::~QHelpEngineCore qhelpenginecore.cpp 240 0x7ffff7b53d2d
12 fulltextsearch::clucene::QHelpSearchIndexWriter::run qhelpsearchindexwriter_clucene.cpp 629 0x7ffff7ba209e
13 QThreadPrivate::start qthread_unix.cpp 298 0x7ffff3d8c3f4
14 start_thread pthread_create.c 304 0x7ffff268aefc
15 clone clone.S 112 0x7ffff350f89d
16 ?? 0