Merge pull request #4 from joanhey/patch-1

fix: update PrettyPageHandler.php fix explicit nullable

Author: mychidarko

src/Exception/Handler/PrettyPageHandler.php

@@ -383,7 +383,7 @@ public function addDataTableCallback($label, /* callable */ $callback)
             throw new InvalidArgumentException('Expecting callback argument to be callable');
         }
 
-        $this->extraTables[$label] = function (\Leaf\Exceptions\Inspector $inspector = null) use ($callback) {
+        $this->extraTables[$label] = function (?\Leaf\Exceptions\Inspector $inspector = null) use ($callback) {
             try {
                 $result = call_user_func($callback, $inspector);