fix: minor ts issue

Author: ihar-tsykala

frontend/src/app/modules/policy-engine/policies/policies.component.ts

@@ -960,7 +960,7 @@ export class PoliciesComponent implements OnInit {
                 }]
             },
         });
-        dialogRef.onClose.pipe(takeUntil(this._destroy$)).subscribe((result: string) => {
+        dialogRef?.onClose.pipe(takeUntil(this._destroy$)).subscribe((result: string) => {
             this.loading = true;
             this.policyEngineService
                 .dryRun(element.id, {