Java+jopendocument: NullPointerException when using getCellAt(0,0)

In a Libreoffice Spreadsheet's sheet, I can get access to a Cell, but not to its value. I don't find my error, any feedback is welcome. Here is the code:

import java.io.File;
import java.io.IOException;
import org.jopendocument.dom.spreadsheet.MutableCell;
import org.jopendocument.dom.spreadsheet.Sheet;
import org.jopendocument.dom.spreadsheet.SpreadSheet;

public class MyClass {
	protected Sheet dataSheet;
	protected File dataCalcFile;
	
	public static void main(String[] args) {
		MyClass myClassInstance = new MyClass(); 
		myClassInstance.loadData();
	}

	public void loadData() {
		int numRows=0, numColumnas=0;
		MutableCell cell=null;
		
		try {
			dataCalcFile = new File(""C:\\temp\\Data.ods"");
			dataSheet = SpreadSheet.createFromFile(dataCalcFile).getSheet(0);
            numRows = dataSheet.getRowCount();            
			System.out.println("Number of rows: " + numRows);
			System.out.println("Cell at 0,0: " + dataSheet.getCellAt(0, 0));
			System.out.println("Nullpointer Exception when getting cell value at 0,0: " + dataSheet.getValueAt(0, 0));	// *** THE INFAMOUS ONE ***		
		} catch (Exception e) {
			System.out.println(e);
		}
	}
}

And here is the output at console:

Number of rows: 107
Cell at 0,0: <table:table-cell xmlns:table="urn:oasis:names:tc:opendocument:xmlns:table:1.0" table:style-name="ce1" xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" office:value-type="string" xmlns:calcext="urn:org:documentfoundation:names:experimental:calc:xmlns:calcext:1.0" calcext:value-type="string"><text:p xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0">Carpeta</text:p></table:table-cell>
java.lang.NullPointerException

Just found that:
"Yes, LO 7 switched to OpenDocument 1.3. We're working on supporting it. In the mean time, you can change the format to "1.2 extended". Go to Options, then Load/Save, then General, then ODF format version."

It works for me, but am excited to hear my customers opinion...

I found that it must be some incompatibility between the library jopendocument and the newer versions of Libreoffice (7.x), as the code above:

• Works as expected if the spreadsheet is edited with Libreoffice 6.4.3.2
• Spits the null pointer exception out if the spreadsheet is edited with Libreoffice 7.0.1.2

In some version in between Calc produces an XML not understood by jopendocument.

Instead of using

getValueAt(0, 0), 
you can use 
getCellAt(0, 0).getElement().getValue()

It works for me.