Only calculate column autosize for a cell if it contains data (#2167)

Only calculate column autosize for a cell if it contains data

src/PhpSpreadsheet/Worksheet/Worksheet.php

@@ -757,6 +757,7 @@ class Worksheet implements IComparable
                             $this->getParent()->getCellXfByIndex($cell->getXfIndex())->getNumberFormat()->getFormatCode()
                         );
 
+                        if ($cellValue !== null && $cellValue !== '') {
                             $autoSizes[$this->cellCollection->getCurrentColumn()] = max(
                                 (float) $autoSizes[$this->cellCollection->getCurrentColumn()],
                                 (float) Shared\Font::calculateColumnWidth(
@@ -769,6 +770,7 @@ class Worksheet implements IComparable
                         }
                     }
                 }
+            }
 
             // adjust column widths
             foreach ($autoSizes as $columnIndex => $width) {