QMimeXMLProvider: fix another issue with -no-mimetype-database

The compiler must emit the destructor for the members of a class in an
inline constructor, in case the constructor throws. This won't work in
Qt 5.15 due to QList requiring knowing whether QMimeMagicRuleMatcher is
trivial or not. Another solution would be to use QVector.

Fixes: QTBUG-82547
Change-Id: Ia8b65350cd5d49debca9fffd15f79db872ed7c0c
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/mimetypes/qmimeprovider.cpp

@@ -664,7 +664,15 @@ QMimeXMLProvider::QMimeXMLProvider(QMimeDatabasePrivate *db, InternalDatabaseEnu
 
     load(data, size);
 }
-#endif
+#else // !QT_CONFIG(mimetype_database)
+// never called in release mode, but some debug builds may need
+// this to be defined.
+QMimeXMLProvider::QMimeXMLProvider(QMimeDatabasePrivate *db, InternalDatabaseEnum)
+    : QMimeProviderBase(db, QString())
+{
+    Q_UNREACHABLE();
+}
+#endif // QT_CONFIG(mimetype_database)
 
 QMimeXMLProvider::QMimeXMLProvider(QMimeDatabasePrivate *db, const QString &directory)
     : QMimeProviderBase(db, directory)

src/corelib/mimetypes/qmimeprovider_p.h

@@ -135,13 +135,10 @@ public:
     enum InternalDatabaseEnum { InternalDatabase };
 #if QT_CONFIG(mimetype_database)
     enum : bool { InternalDatabaseAvailable = true };
-    QMimeXMLProvider(QMimeDatabasePrivate *db, InternalDatabaseEnum);
 #else
     enum : bool { InternalDatabaseAvailable = false };
-    QMimeXMLProvider(QMimeDatabasePrivate *db, InternalDatabaseEnum)
-        : QMimeProviderBase(db, QString())
-    { Q_UNREACHABLE(); };
 #endif
+    QMimeXMLProvider(QMimeDatabasePrivate *db, InternalDatabaseEnum);
     QMimeXMLProvider(QMimeDatabasePrivate *db, const QString &directory);
     ~QMimeXMLProvider();