Need better error message when world is not selected

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Try executing a program without selecting a world first.

What is the expected output? What do you see instead?
We see an uninformative message about TypeError.

Please use labels and text to provide additional information.

Original issue reported on code.google.com by andre.ro...@gmail.com on 21 Aug 2013 at 10:20

[GoogleCodeExporter]

Fixed, revision 246

Original comment by andre.ro...@gmail.com on 21 Aug 2013 at 10:38

• Changed state: Fixed

[GoogleCodeExporter]

Need to change back as this does not work properly when one wants to write 
program that does not use robot; in that case, there should not be any need to 
select a world.

Original comment by andre.ro...@gmail.com on 15 Feb 2014 at 9:09

• Changed state: Started

[GoogleCodeExporter]

This has been fixed in new experimental version where a world is always 
selected by default.

Original comment by andre.ro...@gmail.com on 7 Mar 2014 at 2:44

• Changed state: Fixed