How to handle corrupted ipe file? Latex entry error causes corruption

I just started using ipe for making simple diagrams. Sometimes when
I enter wrong Latex code (in the text dialog), ipe file gets
corrupted. I am not able to delete the bad Latex or edit it anymore
or even select it to edit and delete it. This happened more
than one time.

Here is an example ipe file I am now having problem with fixing

http://12000.org/tmp/oct_4_2015/

The file is p3.ipe in the above folder.

The bad Latex code is the text at the lowest part of the diagram.
I must have typed wrong Latex command there.

How to fix this? As I said, I can't select the bad Latex to
delete it. I click on it, and nothing happens. So I am stuck now.

I am using 7.1.8 on windows 7, 64 bit home edition.

thanks,
--Nasser