Fix various problems

src/Spout/Writer/XLSX/Helper/SharedStringsHelper.php

@@ -25,6 +25,9 @@ EOD;
      */
     const DEFAULT_STRINGS_COUNT_PART = 'count="9999999999999" uniqueCount="9999999999999"';
 
+    /** @var resource Pointer to the sharedStrings.xml file */
+    protected $sharedStringsFilePointer;
+
     /** @var int Number of shared strings already written */
     protected $numSharedStrings = 0;
 

src/Spout/Writer/XLSX/Sheet.php

@@ -21,7 +21,7 @@ class Sheet
     /**
      * @param int $sheetIndex Index of the sheet, based on order of creation (zero-based)
      */
-    function __construct($sheetIndex)
+    public function __construct($sheetIndex)
     {
         $this->index = $sheetIndex;
         $this->name = self::DEFAULT_SHEET_NAME_PREFIX . ($sheetIndex + 1);