[DX] more helpful exception message in case of invalid value

src/Spout/Writer/ODS/Manager/WorksheetManager.php

@@ -243,7 +243,9 @@ private function getCellXML(Cell $cell, $styleIndex, $numTimesValueRepeated)
         } elseif ($cell->isEmpty()) {
             $data .= '/>';
         } else {
-            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . \gettype($cell->getValue()));
+            $value = $cell->getValueEvenIfError();
+
+            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . (\is_object($value) ? \get_class($value) : \gettype($value)));
         }
 
         return $data;

src/Spout/Writer/XLSX/Manager/WorksheetManager.php

@@ -253,7 +253,9 @@ private function getCellXML($rowIndexOneBased, $columnIndexZeroBased, Cell $cell
                 $cellXML = '';
             }
         } else {
-            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . \gettype($cell->getValue()));
+            $value = $cell->getValueEvenIfError();
+
+            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . (\is_object($value) ? \get_class($value) : \gettype($value)));
         }
 
         return $cellXML;