Add phpstan to CI, and fix error

Author: samwilson

composer.json

@@ -14,6 +14,7 @@
     "require-dev": {
         "phan/phan": "^5.4",
         "phpunit/phpunit": "^9.5",
+        "phpstan/phpstan": "^1.8",
         "symfony/var-dumper": "^5.4",
         "unleashedtech/php-coding-standard": "^3.1"
     },
@@ -40,7 +41,8 @@
             "@phpcs",
             "@phpunit",
             "@php examples/basic.php",
-            "phan"
+            "phan",
+            "phpstan analyse --level=8 src/ tests/"
         ]
     }
 }

src/Shortcode.php

@@ -30,7 +30,11 @@ public function getName(): string
 
     public function loadAttrsFromString(string $string): void
     {
-        $parts        = \preg_split('/(?<!\\\\)\\|/', $string);
+        $parts = \preg_split('/(?<!\\\\)\\|/', $string);
+        if (! $parts) {
+            return;
+        }
+
         $unnamedIndex = 1;
         foreach ($parts as $part) {
             if ($part === '') {