Fix JSON crashinfo exception object address

Author: Mike McLaughlin

src/coreclr/nativeaot/System.Private.CoreLib/src/System/CrashInfo.cs

@@ -170,7 +170,8 @@ private bool WriteExceptionHelper(ReadOnlySpan<byte> key, Exception exception, i
             if (!OpenValue(key, '{'))
                 return false;
 
-            if (!WriteHexValue("address"u8, (ulong)Unsafe.AsPointer(ref exception)))
+            ulong address = Unsafe.As<Exception, nuint>(ref exception);
+            if (!WriteHexValue("address"u8, address))
                 return false;
 
             if (!WriteHexValue("hr"u8, exception.HResult))