fn_trace_gettable() reports an error
The most common error codes when tracing regular query execution will be 0, 1 or 2.

0 = OK, 1 = Error, 2 = Abort


Source

In your case, error code 2 = abort, meaning that a query was cancelled due to such things as a timeout or a user action.

You can test this by starting a trace, running a query and stopping it before execution end:



The official definition shows that other error messages might be shown dependent on which events you select:



The same is true for the docs on traces.



These errors and their definition can be found in:

SELECT * 
FROM sys.sysmessages;




Testing this could be done by selecting error events:



Running a divide by zero query to produce an error:



Finding the exception error number:



And then querying sys.sysmessages:

SELECT * 
FROM sys.sysmessages
where error = 8134;


Result: