IllegalArgumentException: invalid property name ''

java.lang.IllegalArgumentException: invalid property name ''

	at org.apache.any23.extractor.microdata.ItemProp.<init>(ItemProp.java:51)
	at org.apache.any23.extractor.microdata.MicrodataParser.getItemProps(MicrodataParser.java:410)
	at org.apache.any23.extractor.microdata.MicrodataParser.getItemScope(MicrodataParser.java:486)
	at org.apache.any23.extractor.microdata.MicrodataParser.getPropertyValue(MicrodataParser.java:346)
	at org.apache.any23.extractor.microdata.MicrodataParser.getItemProps(MicrodataParser.java:403)
	at org.apache.any23.extractor.microdata.MicrodataParser.getItemScope(MicrodataParser.java:486)
	at org.apache.any23.extractor.microdata.MicrodataParser.getMicrodata(MicrodataParser.java:197)
	at org.apache.any23.extractor.microdata.MicrodataParser.getMicrodata(MicrodataParser.java:214)
	at org.apache.any23.extractor.microdata.MicrodataExtractor.run(MicrodataExtractor.java:89)
	at org.apache.any23.extractor.microdata.MicrodataExtractor.run(MicrodataExtractor.java:60)
	at org.apache.any23.extractor.SingleDocumentExtraction.runExtractor(SingleDocumentExtraction.java:480)
	at org.apache.any23.extractor.SingleDocumentExtraction.run(SingleDocumentExtraction.java:259)
	at org.apache.any23.extractor.SingleDocumentExtraction.run(SingleDocumentExtraction.java:323)