Enhance null-checks for various components - #974

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-dotnet@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Possible null reference assignment.

Non-nullable field 'addGenericMethod' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Possible null reference argument for parameter 'target' in 'void PacketHandlerInvoker.Invoke(object target, ByteReader data)'.

Possible null reference assignment.

Converting null literal or possible null value to non-nullable type.

Possible null reference assignment.

Converting null literal or possible null value to non-nullable type.

Dereference of a possibly null reference.

Possible null reference return.

ProjectReference '/home/runner/work/Multiplayer/Multiplayer/Source/Common/Common.csproj' was resolved using '.NETFramework,Version=v4.8' instead of the project target framework '.NETCoreApp,Version=v8.0'. This project may not be fully compatible with your project.

The switch expression does not handle some values of its input type (it is not exhaustive) involving an unnamed enum value. For example, the pattern '(Multiplayer.Common.DevModeScope)2' is not covered.

Dereference of a possibly null reference.

Non-nullable field 'addGenericMethod' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Possible null reference assignment.

Possible null reference assignment.

Possible null reference return.

Possible null reference assignment.

Converting null literal or possible null value to non-nullable type.

Possible null reference assignment.

Converting null literal or possible null value to non-nullable type.

Converting null literal or possible null value to non-nullable type.

Possible null reference assignment.

Converting null literal or possible null value to non-nullable type.

Possible null reference assignment.

Possible null reference assignment.

The switch expression does not handle some values of its input type (it is not exhaustive) involving an unnamed enum value. For example, the pattern '(Multiplayer.Common.DevModeScope)2' is not covered.

Dereference of a possibly null reference.

Converting null literal or possible null value to non-nullable type.

Possible null reference assignment.