[gnome-shell] extensionDownloader: Only check updates for user extensions

[verdre <jonasd src gnome org>]

commit cbc9bc5fc664568184f8b737341e55df136d94a4
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Jan 22 15:42:06 2020 +0100

    extensionDownloader: Only check updates for user extensions
    
    System extensions cannot be updated through the website, so don't
    even try.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/945

 js/ui/extensionDownloader.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/extensionDownloader.js b/js/ui/extensionDownloader.js
index 2ae64ea44d..25145564d7 100644
--- a/js/ui/extensionDownloader.js
+++ b/js/ui/extensionDownloader.js
@@ -120,7 +120,10 @@ function downloadExtensionUpdate(uuid) {
 function checkForUpdates() {
     let metadatas = {};
     Main.extensionManager.getUuids().forEach(uuid => {
-        metadatas[uuid] = Main.extensionManager.lookup(uuid).metadata;
+        let extension = Main.extensionManager.lookup(uuid);
+        if (extension.type !== ExtensionUtils.ExtensionType.PER_USER)
+            return;
+        metadatas[uuid] = extension.metadata;
     });
 
     let params = { shell_version: Config.PACKAGE_VERSION,