ERROR TypeError: Cannot read properties of undefined (reading 'open')

at HeaderComponent.logout (header.component.ts:72:22)

@ViewChild("logoutmodal", { static: true }) logoutModal: ClrModal;

@ViewChild("aboutmodal", { static: true }) aboutModal: ClrModal;

public logout() {

this.logoutModal.open();

}

public about() {

this.aboutModal.open();

}