Add preventive measure to check for null python traceback for clr bubbled exceptions

Author: jhonabreul

src/runtime/PythonException.cs

@@ -187,7 +187,8 @@ private static Exception FromPyErr(BorrowedReference typeRef, BorrowedReference
             if (exception is not null)
             {
                 // Return ClrBubbledExceptions when they are bubbled from Python -> C# -> Python -> C# -> ...
-                if (exception is ClrBubbledException)
+                // or when the traceback is not available, so we fall back  to the original behavior
+                if (exception is ClrBubbledException || traceback is null)
                 {
                     return exception;
                 }