Handle non-existing layers

[grzesiek2010]

Closes #6176

Why is this the best possible solution? Were any other approaches considered?

If the selected layer does not exist anymore it should be cleared and the none option should be selected in offline layers.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

This should only fix the issue and have no side effects.

Do we need any specific form for testing your changes? If so, please attach one.

No.

Does this change require updates to documentation? If so, please file an issue here and include the link below.

No.

Before submitting this PR, please make sure you have:

• added or modified tests for any new or changed behavior
• run ./gradlew connectedAndroidTest (or ./gradlew testLab) and confirmed all checks still pass
• added a comment above any new strings describing it for translators
• added any new strings with date formatting to DateFormatsTest
• verified that any code or assets from external sources are properly credited in comments and/or in the about file.
• verified that any new UI elements use theme colors. UI Components Style guidelines

[srujner]

Tested with Success!

Verified on device with Android 13

Verified cases:

• Issue is no longer reproducing;
• Regression check on Maps;
• Offline Layers tested in General;
• Different Map sources;

[dbemke]

Tested with Success!

Verified on device with Android 10