remove duplicated null replacements

src/sensitiveMessageFormatter.php

@@ -53,11 +53,11 @@ class sensitiveMessageFormatter extends MessageFormatter
         array_map(
             function ($search) use (&$replacements) {
                 $replacements[$search] = str_repeat(
-                    $this->replaceChar ?? '*', 
+                    $this->replaceChar, 
                     $this->fixedReplacementLength ?? strlen($search)
                 );
                 $replacements[urlencode($search)] = str_repeat(
-                    $this->replaceChar ?? '*', 
+                    $this->replaceChar, 
                     $this->fixedReplacementLength ?? strlen($search)
                 );
             },