Platform compatibility analyzer crashes for some platform attributes combinations

[buyaa-n]

Platform compatibility analyzer crashes for some platform attributes combinations

Diagnostic ID: CA1416: Validate Platform compatibility

Analyzer source

SDK: Built-in CA analyzers in .NET 5 SDK or later

Version: Any version above SDK 5.0.100

Describe the bug

Test code to repro:

using System.Runtime.Versioning;

[SupportedOSPlatform("ios10.0")]
static class Program
{
    public static void Main()
    {
        Some.Api1(); // should warn
    }
}

[SupportedOSPlatform("ios10.0")]
[SupportedOSPlatform("tvos10.0")]
[SupportedOSPlatform("macos10.14")]
[SupportedOSPlatform("maccatalyst13.1")]
[UnsupportedOSPlatform("watchos")]
class Some
{
    [UnsupportedOSPlatform("watchos")]
    [UnsupportedOSPlatform("tvos")]
    [UnsupportedOSPlatform("macos")]
    [SupportedOSPlatform("ios14.0")]
    public static void Api1() {}
}

Steps To Reproduce

1. Copy above code in env where CA1416 is enabled
2. Build it
3. Build occasionally fails/crashes

Expected behavior

Should see CA1416 warning

Actual behavior

Build sometimes crushes with AD0001 error

 Analyzer 'Microsoft.NetCore.Analyzers.InteropServices.PlatformCompatibilityAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. 

Related to dotnet/maui#823

[buyaa-n]

CC @jeffhandley