fix null field

Illuminate\Contracts\Encryption\DecryptException: The payload is invalid.
#0 /xxx/vendor/laravel/framework/src/Illuminate/Encryption/Encrypter.php(136): Illuminate\Encryption\Encrypter->getJsonPayload(NULL)
#1 /xxx/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php(261): Illuminate\Encryption\Encrypter->decrypt(NULL)
#2 /xxx/app/Models/EncryptableDbAttribute.php(152): Illuminate\Support\Facades\Facade::__callStatic('decrypt', Array)

Author: safly

src/Traits/EncryptableDbAttribute.php

@@ -30,7 +30,7 @@ public function getAttributeValue($key)
         }
 
         // decrypt value before casts
-        if (in_array($key, $this->encryptable)) {
+        if (in_array($key, $this->encryptable) && !is_null($value) && $value !== '') {
             $value = $this->decrypt($value);
         }