Handle null return from mb_ereg_replace in TextNode

Adds a check for null return value from mb_ereg_replace to throw a LogicalException when invalid encoding is encountered, improving error handling in text cleaning.

https: //github.com/paquettg/pull/260
Co-Authored-By: Gemini_13 <6113770+gemini1389@users.noreply.github.com>

Author: mr-chetan

src/PHPHtmlParser/Dom/Node/TextNode.php

@@ -58,6 +58,11 @@ public function __construct(string $text, $removeDoubleSpace = true)
             if ($replacedText === false) {
                 throw new LogicalException('mb_ereg_replace returns false when attempting to clean white space from "' . $text . '".');
             }
+
+            if ($replacedText === null) {
+                throw new LogicalException('mb_ereg_replace encountered an invalid encoding for "' . $text . '".');
+            }
+
             $text = $replacedText;
         }