prevent unlink errors instead of attempting to suppress them (#48)

even with @, unlink still throws warnings if the file is not found, so we need to check file existence before trying to unlink it

Co-authored-by: John Hunt <[email protected]>

Author: ttgrules

Spreadsheet/Excel/Writer/Worksheet.php

@@ -774,7 +774,7 @@ public function getData($cleanup = true)
                     fclose($this->_filehandle);
                     $this->_filehandle = '';
                 }
-                @unlink($this->_tmp_file);
+                file_exists($this->_tmp_file) && @unlink($this->_tmp_file);
                 $this->_tmp_file      = '';
                 $this->_using_tmpfile = false;
                 $this->_datasize = 0;