Fix some potential NPEs when session is null

[bilal-alsharifi]

Fixes #1781

This PR is ready for review.

Risk

This PR makes no 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

Summary

This PR fixes some potential NPEs that could happen if functions from session are called when the object is null.

CLA

• I have signed the CLA

[codecov]

Codecov Report

Merging #1784 (1c1930f) into develop (b51cda0) will decrease coverage by 0.06%.
The diff coverage is 9.85%.

❗ Current head 1c1930f differs from pull request most recent head 85e7f29. Consider uploading reports for the commit 85e7f29 to get more accurate results

@@              Coverage Diff              @@
##             develop    #1784      +/-   ##
=============================================
- Coverage      54.39%   54.32%   -0.07%     
- Complexity      5516     5521       +5     
=============================================
  Files            562      562              
  Lines          25543    25590      +47     
  Branches        3328     3338      +10     
=============================================
+ Hits           13893    13903      +10     
- Misses         10391    10424      +33     
- Partials        1259     1263       +4     

Impacted Files	Coverage Δ
...elink/managers/lifecycle/BaseLifecycleManager.java	13.76% <9.85%> (-0.22%)	⬇️
...smartdevicelink/encoder/VirtualDisplayEncoder.java	44.91% <0.00%> (-0.36%)	⬇️
...ink/managers/screen/BaseTextAndGraphicManager.java	64.16% <0.00%> (+0.41%)	⬆️
...rtdevicelink/streaming/video/SdlRemoteDisplay.java	50.00% <0.00%> (+6.09%)	⬆️

[RHenigan]

These changes look good, I think the only thing we need to add is we should wrap the initialization of session in a synchronized block as well. Can you also add a new comment or update the existing comment to better capture what changes this PR makes?

[noah-livio]

These changes look good, I think the only thing we need to add is we should wrap the initialization of session in a synchronized block as well. Can you also add a new comment or update the existing comment to better capture what changes this PR makes?

Sounds good, I'll make that change, and yeah I'll add a new comment to better reflect the current changes

[noah-livio]

Fixes #1781

This PR is ready for review.

Risk

This PR makes no 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

Summary

This PR ensures all access to session in BaseLifecycleManager and LifecycleManager is synchronized and protected using null checks to prevent NPEs related to session from occurring.

CLA

• I have signed the CLA