Fix for vUndefined errors when upgrading

CHANGELOG.md

@@ -6,6 +6,7 @@
 1. [](#bugfix)
     * Missed a `CacheCommand` reference in `bin/grav` [#2442](https://github.com/getgrav/grav/issues/2442)
     * Fixed issue with `Utils::normalizePath` messing with external URLs [#2216](https://github.com/getgrav/grav/issues/2216)
+    * Fix for `vUndefined` versions when upgrading
 
 # v1.6.2
 ## 04/11/2019

system/src/Grav/Common/GPM/Remote/Package.php

@@ -12,11 +12,16 @@ namespace Grav\Common\GPM\Remote;
 use Grav\Common\Data\Data;
 use Grav\Common\GPM\Common\Package as BasePackage;
 
-class Package extends BasePackage
+class Package extends BasePackage implements \JsonSerializable
 {
     public function __construct($package, $package_type = null)
     {
         $data = new Data($package);
         parent::__construct($data, $package_type);
     }
+
+    public function jsonSerialize()
+    {
+        return $this->data;
+    }
 }