[#3192] - iReport Creates Malformed JRXML when Cells are deleted in Table Elements

When using iReport 5.1.0 deleting a cell may be required to achieve the visual output required. However, when deleting a cell within iReport it is deleting the JRXML reference, when in reality we just need the cell to be zero height since its inclusion in the XSD is noted as required.

Steps to Reproduce
1. Create new JRXML file.
2. Add Table Element.
3. Right-Click and delete cells, leave the top row.
4. Compile.
5. Save the JRXML file.
6. Close JRXML tab in iReport.
7. Open JRXML, failure occurs.
8. Open compiled JASPER file, the file is converted but the resultant JRXML has schema errors.