Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Worksheet/ColumnCellIterator.php
protected function adjustForExistingOnlyRange()
    {
        if ($this->onlyExistingCells) {
            while ((!$this->worksheet->cellExistsByColumnAndRow($this->columnIndex, $this->startRow)) &&
                ($this->startRow <= $this->endRow)) {
                ++$this->startRow;
            }
            if ($this->startRow > $this->endRow) {
                throw new PhpSpreadsheetException('No cells exist within the specified range');
            }
            while ((!$this->worksheet->cellExistsByColumnAndRow($this->columnIndex, $this->endRow)) &&
                ($this->endRow >= $this->startRow)) {
                --$this->endRow;
            }
            if ($this->endRow < $this->startRow) {
                throw new PhpSpreadsheetException('No cells exist within the specified range');
            }
        }
    }
protected function adjustForExistingOnlyRange()
    {
        if ($this->onlyExistingCells) {
            while ((!$this->worksheet->cellExistsByColumnAndRow($this->columnIndex, $this->startRow)) &&
                ($this->startRow <= $this->endRow)) {
                ++$this->startRow;
            }
            if ($this->startRow > $this->endRow) {
                throw new PhpSpreadsheetException('No cells exist within the specified range');
            }
            while ((!$this->worksheet->cellExistsByColumnAndRow($this->columnIndex, $this->endRow)) &&
                ($this->endRow >= $this->startRow)) {
                --$this->endRow;
            }
            if ($this->endRow < $this->startRow) {
                throw new PhpSpreadsheetException('No cells exist within the specified range');
            }
        }
    }
Validate start/end values for "IterateOnlyExistingCells" mode, and adjust if necessary.

@throws PhpSpreadsheetException