if null, default to empty string

Author: dododedodonl

resources/lang/en/messages.php

@@ -1,6 +1,7 @@
 <?php
 
 return [
+    'must-be-string' => ':Attribute must be a string or null',
     'error-message' => 'JSON validaton failed for :attribute.',
     'detailed-error-message' => 'JSON validation failed for :attribute. :details',
 ];

src/Rules/BaseRule.php

@@ -27,6 +27,12 @@ public function __construct(
      */
     public function validate(string $attribute, mixed $value, Closure $fail): void
     {
+        $value ??= '';
+
+        if (! is_string($value)) {
+            $fail('json-schema::messages.must-be-string')->translate(['attribute' => $attribute]);
+        }
+
         $result = $this->schemaValidator->validate($this->determineSchemaName(), $value);
 
         if ($result->failed()) {