fix tooltips not working with shortcode

[Deji98]

Description

fix tooltips not working with shortcode:
Resolved falling back to default when custom_title isn't set even though custom_title_zero and custom_title_plural is
Ensured there's a default when either or none is set

Benefits

fix #102

Possible drawbacks

Applicable issues

#102

Checklist

• I have created a specific branch for this pull request before committing, starting off the current HEAD of development branch.
• I'm submitting to the development, feature/hotfix/release branch. (Do not submit to the master branch!)
• This pull request relates to a specific problem (bug or improvement).
• I have mentioned the issue number in the pull request description text.
• All the issues mentioned in this pull request relate to the problem I'm trying to solve.
• The code I'm sending follows the PSR-12 coding style.