Background and border color transparency support for textboxes when color is undefined

Author: Chudy20007

src/PhpWord/Writer/Word2007/Element/TextBox.php

@@ -50,6 +50,13 @@ public function write(): void
 
         if ($style->getBgColor()) {
             $xmlWriter->writeAttribute('fillcolor', $style->getBgColor());
+        } else {
+            $xmlWriter->writeAttribute('filled', 'f');
+        }
+
+        if (!$style->getBorderColor()) {
+            $xmlWriter->writeAttribute('stroked', 'f');
+            $xmlWriter->writeAttribute('strokecolor', 'white');
         }
 
         $styleWriter->write();