Problem

When you type something on iOS, page will be scrolled to top.

Fixes #2689
Possible fixes #2261

Cause

Due to lack of the "strict" mode in the tsconfig there was a missed problem in the "scroll-locker.ts" class.

The iOS-specific method unlockHard() (called from the Popover' hide() which is being called every keydown) checks for null, but this.scrollPosition was undefined initially

  /**
   * Unlocks hard scroll lock
   */
  private unlockHard(): void {
    document.body.classList.remove(ScrollLocker.CSS.scrollLockedHard);
    if (this.scrollPosition !== null) { 
      window.scrollTo(0, this.scrollPosition);
    }
    this.scrollPosition = null;
  }

Solution

1. I initialized this.scrollPosition with null explicitly.
2. Additionally, I updated the PopoverMobile's hide() method. Now it won't trigger any logic if popover is already hidden (to prevent possible layout caused by CSS classes adding)