QTextTabel: column width changes when merging other rows

When merging row [1]  into one cell the width of column 1 gets changed:

becomes

Code: 

QTextDocument* td =ui->te->document();
td->clear();
QTextCursor tc(td);

tc.movePosition(QTextCursor::MoveOperation::End);
QTextTable* table =tc.insertTable(3, 3);

int row =0;
QTextTableCell c00 =table->cellAt(row, 0);
QTextTableCell c01 =table->cellAt(row, 1);
QTextTableCell c02 =table->cellAt(row, 2);

c00.firstCursorPosition().insertText(QStringLiteral("Header 0"));
c01.firstCursorPosition().insertText(QStringLiteral("Header 1"));
c02.firstCursorPosition().insertText(QStringLiteral("Header 2"));
// this goes bad
table->mergeCells(1,0, 1, 3);