extensionSystem: Update canChange on error

Whether or not an extension has errors influences the 'canChange'
property, but so far we only update it for errors that occur when
initializing the extension, not when an extension is enabled later.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1249


(cherry picked from commit 3309031fd1)

js/ui/extensionSystem.js

@@ -269,6 +269,7 @@ var ExtensionManager = class {
         extension.errors.push(message);
 
         logError(error, 'Extension %s'.format(uuid));
+        this._updateCanChange(extension);
         this.emit('extension-state-changed', extension);
     }