How to manage merged cells in BIRT?

Question

I am using BIRT 3.7.2 with Spudsoft emitter to create xlsx output from a report. If I merge 2 cells in the report designer, the output file xl/worksheets/sheet1.xml contains this:

<mergeCells> <mergeCell ref="A24:B24"/> <mergeCell ref="A24:B24"/> </mergeCells>

I guess it's bad to have the same line duplicated and MS Excel 2010 also gives a warning when I try to open it. If I manually delete one of those lines it doesn't give any warnings anymore.

Any ideas on why is that line duplicated? I can't find the bug.