Remove any dependency on dockmanager in desktopIconsIntegration.js

Dockmanager can be null, and this spams the log if desktopIconsIntegration class
is initialized and used.

desktopIconsIntegration class is initialized and called from the extension and
really should not have any other dependencies other than the shell,
it is meant to be used and can be used as is by any extension if called as is
independently without modifications.

desktopIconsIntegration.js

@@ -58,13 +58,14 @@
 import {GLib} from './dependencies/gi.js';
 import {Main} from './dependencies/shell/ui.js';
 import {ExtensionUtils} from './dependencies/shell/misc.js';
-
-import {DockManager} from './docking.js';
+import {Extension} from './dependencies/shell/extensions/extension.js';
 
 const IDENTIFIER_UUID = '130cbc66-235c-4bd6-8571-98d2d8bba5e2';
 
 export class DesktopIconsUsableAreaClass {
     constructor() {
+        const Me = Extension.lookupByURL(import.meta.url);
+        this._UUID = Me.uuid;
         this._extensionManager = Main.extensionManager;
         this._timedMarginsID = 0;
         this._margins = {};
@@ -158,7 +159,7 @@ export class DesktopIconsUsableAreaClass {
         const usableArea = extension?.stateObj?.DesktopIconsUsableArea;
         if (usableArea?.uuid === IDENTIFIER_UUID) {
             usableArea.setMarginsForExtension(
-                DockManager.extension.uuid, this._margins);
+                this._UUID, this._margins);
         }
     }
 }