fix(label-group): wrap #labels getter with server check to avoid DOM access in SSR

Author: Sara Dahan

elements/pf-label-group/pf-label-group.ts

@@ -108,10 +108,15 @@ export class PfLabelGroup extends LitElement {
   })
   private _categorySlotted?: HTMLElement[];
 
-  get #labels(): NodeListOf<PfLabel> {
+  get #labels(): NodeListOf<PfLabel> | PfLabel[] {
+    const isServer = typeof window === 'undefined' || !('document' in globalThis);
+    if (isServer) {
+      return [] as PfLabel[];
+    }
     return this.querySelectorAll<PfLabel>('pf-label:not([slot]):not([overflow-label])');
   }
 
+
   #tabindex = RovingTabindexController.of(this, {
     getItems: () => [
       ...Array.prototype.slice.call(