fix(core): update

ts/domtools.classes.thememanager.ts

@@ -4,7 +4,7 @@ import * as plugins from './domtools.plugins';
 
 export class ThemeManager {
   public domtoolsRef: DomTools;
-  
+
   public goBrightBoolean = false;
   public preferredColorSchemeMediaMatch = window.matchMedia('(prefers-color-scheme: light)');
 
@@ -15,7 +15,7 @@ export class ThemeManager {
 
     // lets care
     this.goBrightBoolean = this.preferredColorSchemeMediaMatch.matches;
-    this.preferredColorSchemeMediaMatch.addEventListener('change', eventArg => {
+    this.preferredColorSchemeMediaMatch.addEventListener('change', (eventArg) => {
       this.goBrightBoolean = eventArg.matches;
       this.updateAllConnectedElements();
     });
@@ -23,7 +23,9 @@ export class ThemeManager {
   }
 
   private async updateAllConnectedElements() {
-    document.body.style.background = this.goBrightBoolean ? '#fff' : '#000';
+    if (document.body && document.body.style) {
+      document.body.style.background = this.goBrightBoolean ? '#fff' : '#000';
+    }
     this.themeObservable.next(this.goBrightBoolean);
   }
 
@@ -41,4 +43,4 @@ export class ThemeManager {
     this.goBrightBoolean = !this.goBrightBoolean;
     this.updateAllConnectedElements();
   }
-}
+}