Add comment on detach use

src/core/qgsogrutils.cpp

@@ -226,8 +226,12 @@ QVariant QgsOgrUtils::getOgrFeatureAttribute( OGRFeatureH ogrFet, const QgsField
       {
         int size = 0;
         const GByte *b = OGR_F_GetFieldAsBinary( ogrFet, attIndex, &size );
+
+        // QByteArray::fromRawData is funny. It doesn't take ownership of the data, so we have to explicitly call
+        // detach on it to force a copy which owns the data
         QByteArray ba = QByteArray::fromRawData( reinterpret_cast<const char *>( b ), size );
         ba.detach();
+
         value = ba;
         break;
       }