Fix primary key usage with different types

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Db/Group.php

@@ -24,11 +24,12 @@
 namespace OCA\Deck\Db;
 
 use OCP\IGroup;
+use OCP\Share\IShare;
 
 class Group extends RelationalObject {
 
 	public function __construct(IGroup $group) {
-		$primaryKey = $group->getGID();
+		$primaryKey = IShare::TYPE_GROUP . ':' . $group->getGID();
 		parent::__construct($primaryKey, $group);
 	}
 
@@ -38,4 +39,4 @@ class Group extends RelationalObject {
 			'displayname' => $this->object->getDisplayName()
 		];
 	}
-}
+}