Fix/slot undefined error

[darylldoyle]

Description of the Change

There are two bug fixes in this PR.

Another initializeSlotData() error

initializeSlotData() expects an event rather than a Slot. This PR changes out a call that was still passing the slot.

Uncaught TypeError: Cannot read property 'toString' of undefined error

Within isEligible() we were using event.size.toString(). It seems that the size property is only actually available on the googletag.events.slotrenderendedevent event. So when the isEligible() function was being called using googletag.events.slotvisibilitychangedevent or googletag.events.impressionviewableevent, it was erroring with a "Uncaught TypeError: Cannot read property 'toString' of undefined" error.

This PR also fixes this issue by checking if event.size exists before attempting to access it.

Verification Process

Tested on local and preprod environments.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

#38

Changelog Entry

[davidrgreen]

@darylldoyle Thanks for catching and fixing this!