What changes were made in MvvmCross 6.2.2 that might impact null reference exceptions

1. IoC Provider Initialization: One significant change relates to the initialization of the `Mvx.IoCProvider`. Prior to this version, if the IoC provider was not set up correctly, it could lead to null reference exceptions when constructing commands like `MvxAsyncCommand` in view models. The constructor for `MvxCommandBase` was updated to include a fallback mechanism that uses `MvxWeakCommandHelper` if the IoC provider is null or fails to resolve an instance of `IMvxCommandHelper`. This change aims to mitigate NREs by ensuring that commands can still function even if the IoC provider is not fully initialized[1].

2. Error Handling Improvements: The handling of potential null references has been improved in various parts of the framework. For instance, checks have been added to ensure that certain properties and methods do not attempt to dereference null objects. This is particularly relevant for components that rely on external services or dependencies that may not always be available[1].

3. Unit Testing Adjustments: Users reported issues with unit tests failing due to null reference exceptions when using `MvxAsyncCommand`. The recommendation was made to explicitly initialize the IoC provider in unit test projects. This adjustment helps ensure that all dependencies are properly resolved before executing tests, thereby reducing the likelihood of encountering NREs during testing scenarios[1].

4. General Bug Fixes: The release notes for MvvmCross 6.2.2 indicate that a number of bugs related to null reference exceptions were addressed, although specific details on each fix were not extensively documented. These fixes may include adjustments across various components of the framework where NREs were previously reported[10].

Overall, these changes in MvvmCross 6.2.2 focus on improving the stability and reliability of command execution and dependency resolution, which are critical areas where null reference exceptions can arise. By enhancing the initialization process and error handling, developers can expect a reduction in such exceptions in their applications built with this framework.