Error in SMW_SQLStore2.php

Fatal error: Call to a member function setId() on a non-object in /home/samuel/www/smw-trunk/extensions/SemanticMediaWiki/includes/storage/SMW_SQLStore2.php on line 1975
Call Stack
#   Time    Memory  Function    Location
1   0.0231  377804  {main}( )   ../index.php:0
2   1.1009  10096504    MediaWiki->run( )   ../index.php:58
3   1.1010  10096504    MediaWiki->main( )  ../Wiki.php:529
4   1.1015  10096580    MediaWiki->performRequest( )    ../Wiki.php:622
5   1.1041  10217500    SpecialPageFactory::executePath( ???, ???, ??? )    ../Wiki.php:221
6   1.1536  12292880    RDFImport->execute( ??? )   ../SpecialPageFactory.php:467
7   1.3234  19172304    RDFImport->executeSMWBatchWriter( ) ../SpecialRDFImport_body.php:60
8   1.3234  19172304    RDFIOSMWBatchWriter->execute( ) ../SpecialRDFImport_body.php:101
9   2.2246  21899376    RDFIOSMWBatchWriter->writePagesToWiki( )    ../SMWBatchWriter.php:96
10  2.2247  21900716    RDFIOPageHandler->writeOrDeleteDataToWiki( ??? )    ../SMWBatchWriter.php:282
11  2.2744  23757516    SMWDataValueFactory::newPropertyObjectValue( ???, ???, ??? )    ../PageHandler.php:53
12  2.2744  23757560    SMWDataValueFactory::newTypeIdValue( ???, ???, ???, ??? )   ../SMW_DataValueFactory.php:166
13  2.2758  23838364    SMWDataValue->setUserValue( ???, ??? )  ../SMW_DataValueFactory.php:103
14  2.2766  23869984    SMWDataValue->checkAllowedValues( ) ../SMW_DataValue.php:166
15  2.2778  23876160    SMWSQLStore2->getPropertyValues( ???, ???, ??? )    ../SMW_DataValue.php:700
16  2.2779  23876428    SMWSQLStore2->getSemanticData( ???, ??? )   ../SMW_SQLStore2.php:198
17  2.2780  23876544    SMWSQLStore2->getSMWPageIDandSort( ???, ???, ???, ???, ???, ??? )   ../SMW_SQLStore2.php:127