try to avoid NPE for currentConversation

[mahibi]

fix #4190

On gplay console the following NPE was reported for the line

participantPermissions = ParticipantPermissions(spreedCapabilities, currentConversation!!)

E FATAL EXCEPTION: main
Process: com.nextcloud.talk2, PID: 6626
java.lang.NullPointerException
at com.nextcloud.talk.chat.ChatActivity.initObservers$lambda$13(ChatActivity.kt:583)
at com.nextcloud.talk.chat.ChatActivity.$r8$lambda$QKH5JCFLmCzRMlSJ-EV-m4IW5ig(Unknown Source:0)

which seems that currentConversation was null. If it would have been spreedCapabilities, then the error would have been thrown in the line before..

A reason MAY BE that the observer is triggered before setData on the ViewModel is executed. While this fix is just not executing code when currentConversation is null, it's unsure if it will follow up problems (like an empty chat) or if the observer is triggered another time when currentConversation is available.

So it's just a hotfix.
To improve the situation in the long term, we should move more logic to viewModel and only use Flow instead to mix it with LiveData.

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	86	96
Errors	131	131

SpotBugs

Category	Base	New
Bad practice	6	6
Correctness	11	11
Dodgy code	79	79
Internationalization	3	3
Malicious code vulnerability	3	3
Performance	6	6
Security	1	1
Total	109	109

Lint increased!

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/4261-talk.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud Talk app.