refactor(theme-shared): add snq for type error

npm/ng-packs/packages/theme-shared/src/lib/components/http-error-wrapper/http-error-wrapper.component.ts

@@ -14,6 +14,7 @@ import {
 } from '@angular/core';
 import { fromEvent, Subject } from 'rxjs';
 import { debounceTime, filter } from 'rxjs/operators';
+import snq from 'snq';
 
 @Component({
   selector: 'abp-http-error-wrapper',
@@ -49,7 +50,8 @@ export class HttpErrorWrapperComponent implements AfterViewInit, OnDestroy, OnIn
   }
 
   ngOnInit() {
-    this.backgroundColor = window.getComputedStyle(document.body).getPropertyValue('background-color');
+    this.backgroundColor =
+      snq(() => window.getComputedStyle(document.body).getPropertyValue('background-color')) || '#fff';
   }
 
   ngAfterViewInit() {