FIX Do not update LeftAndMain link with Stage param

src/VersionedStateExtension.php

@@ -2,6 +2,7 @@
 
 namespace SilverStripe\Versioned;
 
+use SilverStripe\Admin\LeftAndMain;
 use SilverStripe\Control\Controller;
 use SilverStripe\Control\RequestHandler;
 use SilverStripe\Core\Extension;
@@ -48,6 +49,11 @@ public function updateLink(&$link)
             return;
         }
 
+        // Don't touch Admin/CMS links
+        if (class_exists(LeftAndMain::class) && $this->getOwner() instanceof LeftAndMain) {
+            return;
+        }
+
         // Decorate
         $link = Controller::join_links(
             $link,

tests/php/VersionedStateExtensionTest.php

@@ -2,6 +2,7 @@
 
 namespace SilverStripe\Versioned\Tests;
 
+use SilverStripe\Admin\LeftAndMain;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Versioned\Versioned;
 use SilverStripe\Versioned\VersionedStateExtension;
@@ -61,4 +62,19 @@ public function testUpdateLinkRespectsQueryArgs()
             ->byID($obj1ID);
         $this->assertEquals('item/myobject/', $obj1Live->Link());
     }
+
+    public function testDontUpdateLeftAndMainLinks()
+    {
+        $controller = new LeftAndMain();
+
+        $liveClientConfig = $controller->getClientConfig();
+        Versioned::set_stage(Versioned::DRAFT);
+        $stageClientConfig = $controller->getClientConfig();
+
+        $this->assertEquals(
+            $liveClientConfig,
+            $stageClientConfig,
+            'LeftAndMain Client config should not be affected by versionned stage.'
+        );
+    }
 }