Bug:the add-task component won't show normally

[champion0122]

Firstly, i clicked the 'Add' button to show add-task form.

Then, i click the 'About' link to the page about.I couldn't find the add-task form after i go back to the '/' path.

The *ngIf used in add-task component may used the default value set for variable 'showAddTask'(false).

I'm a newbie in angular, i want to know which way to solve it is the angular way.Thanks!

BTW, if we don't use unsubscribe observable in service, the subscribe will perform more than once unexpectedly after we switch the pages.