str_replace(): Passing null to parameter #2 ($replace) of type array|string is deprecated"

src/PhpWord/Escaper/Xml.php

@@ -27,6 +27,6 @@ class Xml extends AbstractEscaper
     protected function escapeSingleValue($input)
     {
         // todo: omit encoding parameter after migration onto PHP 5.4
-        return (!is_null($input)) ? htmlspecialchars($input, ENT_QUOTES, 'UTF-8') : null;
+        return (!is_null($input)) ? htmlspecialchars($input, ENT_QUOTES, 'UTF-8') : '';
     }
 }

src/PhpWord/TemplateProcessor.php

@@ -261,7 +261,7 @@ class TemplateProcessor
             $subject = utf8_encode($subject);
         }
 
-        return $subject;
+        return (!is_null($subject)) ? $subject : '';
     }
 
     /**