Fix saving page without parent via PIP GUI

See #2545

diff --git a/wcfsetup/install/files/lib/system/package/plugin/PagePackageInstallationPlugin.class.php b/wcfsetup/install/files/lib/system/package/plugin/PagePackageInstallationPlugin.class.php
index 6759cc4263da72bd485a3dddd9dce77e49659867..adce82cf0708821238be46dcb719a7da2c490c74 100644 (file)
--- a/wcfsetup/install/files/lib/system/package/plugin/PagePackageInstallationPlugin.class.php
+++ b/wcfsetup/install/files/lib/system/package/plugin/PagePackageInstallationPlugin.class.php
@@ -753,7 +753,9 @@ class PagePackageInstallationPlugin extends AbstractXMLPackageInstallationPlugin
                                $parent = $data['parent'];
                                unset($data['parent']);
                                
-                               $data['parentPageID'] = Page::getPageByIdentifier($parent)->pageID;
+                               if (!empty($parent)) {
+                                       $data['parentPageID'] = Page::getPageByIdentifier($parent)->pageID;
+                               }
                        }
                }