Bugfix/issue #1842 - NPE in BaseTextAndGraphicsManager

[JulianKast]

Fixes #1842

This PR is [ready] for review.

Risk

This PR makes [minor] API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).
• I have tested Android, Java SE, and Java EE

Core Tests

Tested general functionality of each manager touched to ensure they still function.
Then when into each manager and set the transactionQueue to null just before the null checks to ensure no crashes occurred, errors where logged, and callback listeners were triggered.

I also tested setting theFileManager transactionQueue to null while trying other managers that rely on it.

Tested Android Manticore v 2.11.0 and Sync 3
Tested JavaSE core 8.2.0 /sdl_hmi 5.8.0

Summary

This PR adds null checks to prevent NPE's with TaskMaster queues in the manager layers

Changelog

Bug Fixes

• Fixes a reported NPE in BaseTextAndGraphicManager as well as preventing it throughout the manager layer

CLA

• I have signed the CLA