[qt] Fix issue if resources not being found on the database

Once again QVariant getting confused about its contents
datatype. With this patch we use QString directly and
copy the contents, which should be cheap with Qt implicity
sharing.

platform/qt/src/sqlite3.cpp

@@ -270,20 +270,15 @@ void Statement::bind(int offset, optional<mbgl::Timestamp> value) {
     }
 }
 
-void Statement::bind(int offset, const char* value, std::size_t length, bool retain) {
+void Statement::bind(int offset, const char* value, std::size_t length, bool /* retain */) {
     assert(impl);
     if (length > std::numeric_limits<int>::max()) {
         // Kept for consistence with the default implementation.
         throw std::range_error("value too long");
     }
 
-    // Qt SQLite driver treats QByteArray as blob: we need to explicitly
-    // declare the variant type as string.
-    QVariant text(QVariant::Type::String);
-    text.setValue(retain ? QByteArray(value, length) : QByteArray::fromRawData(value, length));
-
     // Field numbering starts at 0.
-    impl->query.bindValue(offset - 1, std::move(text), QSql::In);
+    impl->query.bindValue(offset - 1, QString(QByteArray(value, length)), QSql::In);
 
     checkQueryError(impl->query);
 }