Reader: fix a glitch in the following tab

[yaelirub]

Fixing an issue where the following tab is being initially laid out out off to the left of the screen

Gif of the issue:

To test:

1. Launch the app
2. tap the Reader
3. see that the "Following" tab is not jumping from the left

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[leandroalonso]

@yaelirub this call was added on purpose.

Mainly, to prevent this issue: #14412

I think that if we remove this call and follow the steps described in the issue (fresh install -> Reader) the issue will happen again — and a small glitch is less problematic than waiting (sometimes seconds) for the screen to appear.

[leandroalonso]

@yaelirub I managed to fix.

We need to change this guard: https://github.com/wordpress-mobile/WordPress-iOS/blob/develop/WordPress/Classes/ViewRelated/System/FilterTabBar.swift#L427

Basically, it should be like this:

guard scrollView.contentSize.width > scrollView.frame.width, bounds.width > 0 else {

The issue is happening because this method is trying to do some calculations while the bounds haven't been calculated yet. This solves the issue. :)

[yaelirub]

Thank you so so much, @leandroalonso ! I updated to your recommended. Ready of another look

[yaelirub]

Done in #15536