Wrong rowcount sent via signal

Description

m_last +1 and m_first do not neccessarly represent the rowcount, so use the spreadsheet to read out the rowCount. This happens if a row unequal to the last will be removed or a row will be inserted before the last row.

Conformity

• Changelog entry
• Downport
• Unittests
• Fixes: #613 (closed)

If external dependencies are removed

• Reporting to ...