Transaction failure for deleting stop times.

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create stops; add one stop time;
2. Create route;
3. Create trip; add a stop time;
4. Go back to the stops... and delete the stop time created in `trips'.
5. Now try and delete the stop time created in `stops'

What is the expected output? What do you see instead?
You should be able to delete any stop time. Instead, you can only delete stop 
times that were created from the `trips' side... not those that were created 
and added in `stops'.

Please provide any additional information below.
I guess that we can/should remove the functionality to stop times in `stops'... 
so that they cannot cause errors. But, given the format of some schedules, it 
may be quit useful to add all the stop times (and link them to trips later... 
if that is possible). I'll have a look at the code itself at some stage. 

Original issue reported on code.google.com by johanwjo...@gmail.com on 16 May 2011 at 6:47