extensions-app: Reset switch handle when it becomes insensitive

Currently the switches handle position reflects the requested
extension state (as in: the user (de)activated the switch),
while the actual extension state is reflected by the underlying
state.

That doesn't work well when the switch is insensitive though (for
example on error), because the desaturation neuters the color
that reflects the state.

Address this by resetting the switch handle to the state when
making it insensitive.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1263


(cherry picked from commit d2583aa47b)

subprojects/extensions-app/data/ui/extension-row.ui

@@ -54,7 +54,7 @@
           </object>
         </child>
         <child>
-          <object class="GtkSwitch">
+          <object class="GtkSwitch" id="switch">
             <property name="visible">True</property>
             <property name="can_focus">True</property>
             <property name="valign">center</property>

subprojects/extensions-app/js/main.js

@@ -334,6 +334,7 @@ var ExtensionRow = GObject.registerClass({
         'versionLabel',
         'authorLabel',
         'updatesIcon',
+        'switch',
         'revealButton',
         'revealer',
     ],
@@ -453,6 +454,9 @@ var ExtensionRow = GObject.registerClass({
         action.set_state(new GLib.Variant('b', state));
         action.enabled = this._canToggle();
 
+        if (!action.enabled)
+            this._switch.active = state;
+
         this._updatesIcon.visible = this.hasUpdate;
 
         this._versionLabel.label = this.version.toString();