Analyzer try report diagnostics MsgPack003 on codes that are not from current assembly, and then crash with code AD0001

#### Bug description

If you have an object with [MessagePackObject], and it contains a member without it, the analyzer will report a MsgPack003. Then if that member's type is from another assembly in source code form, it will crash.

#### Repro steps

Open the mrp project I attached, turn on global analysis, and you will see the warning.
Is confirmed with vs and vsc on windows. Not sure about rider and on other os.

#### Expected behavior

No AD0001 warning.

#### Actual behavior

AD0001, which is actually a analyzer crash.

- Version used: MessagePack 3.1.3 from nuget
- Runtime: Net9.0

#### Additional context


[Mrp_MessagePackAnalyzerBug.zip](https://github.com/user-attachments/files/20557228/Mrp_MessagePackAnalyzerBug.zip)

Start with the attached Mrp_MessagePackAnalyzerBug.zip and reproduce the analyzer behavior with MessagePack 3.1.3 on .NET 9.0, using Visual Studio or VS Code with global analysis enabled. Trace the diagnostic path for a member whose type comes from another source assembly; done means the repro no longer produces the AD0001 analyzer crash.

Written by the indexing model from the issue text.