Why is the file /var/crash/_usr_lib_empathy_empathy-chat.1000.upload empty?

I just experienced an unusual crash: I tried to click on a name entry in the contact list of Empathy. A crash happened. Usually I am asked then if I'd like to report the error to Launchpad, and Launchpad opens. This time the error message was:

"Excuse me. Ubuntu 12.04 noticed an internal error. If you notice further problems try to restart your computer. Send an error report to Launchpad to help removing this problem?"

This time Launchpad did not open automatically. A new window opened and I could read the relevant error report. Later I found the error report in the file /var/crash/_usr_lib_empathy_empathy-chat.1000.crash. Why went the course of action this time differently from other crashes? Why is the file /var/crash/_usr_lib_empathy_empathy-chat.1000.upload empty?

This is happening because there is a new default workflow for crashes in stable (i.e., non-development) releases. Instead of asking you to file a bug report with the crash data, the crash data are sent to a server where they are statistically analyzed.

See this question for more information, including rationale and details.

There are a few ways to restore the old behavior, if you wish to. Some are described here and others here. If you want to restore the old behavior of reporting crashes manually by filing Launchpad bugs (even in a stable release)--and there are many reasons you may want to do this, if you're willing to put in the effort to file a good bug report--then I recommend this particular technique:

It works to edit /etc/apport/crashdb.conf and add Crash to the problem_types: ['Bug', 'Package', 'Crash']