Check class type to take care of the case textField.name has "long" type

[t-yoshii]

Fixes #1122

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

I tested with my devboard HU.

Summary

Add a type check in SDLDisplayCapabilities+ShowManagerExtensions#maxNumberOfMainFieldLines.

Changelog

Bug Fixes

• Avoid crash by adding type check at SDLDisplayCapabilities+ShowManagerExtensions#maxNumberOfMainFieldLines.

CLA

• I have signed the CLA

[joeljfischer]

Hi @t-yoshii are there any production units that exhibit this issue? If the issue will be mitigated before any production head units show the issue, it would be preferable to have this fixed on SDL Core instead of creating special case fixes that are not needed.

[t-yoshii]

Hi @joeljfischer ,

Thanks for your comments.
I confirmed that our customer's real HU also hit this issue. Those HUs will be released this December, so we cannot fix HU side (SDL Core or HMI).
In addition, fix for Core requires API change, so, It takes a long time for the permanent fix to be applied.

It would be greatly appreciated if you approve this PR.