OnDemand import fails when export contains demo project data

Import of data from JIRA 5.2.2 to OnDemand fails with the message "This archive doesn't contains any valid avatars" (sic).

The root cause is that the avatars zip file contains some files with .jim extension:

[~/jira/home/data/avatars]$ ll
total 24
drwxr-xr-x  5 shaldane  staff   170 11 Dec 18:19 .
drwxr-xr-x  4 shaldane  staff   136 11 Dec 18:19 ..
-rw-r--r--  1 shaldane  staff  1284 11 Dec 18:19 10200_attachment2871347870287331752.jim
-rw-r--r--  1 shaldane  staff   852 11 Dec 18:19 10200_medium_attachment2871347870287331752.jim
-rw-r--r--  1 shaldane  staff   341 11 Dec 18:19 10200_small_attachment2871347870287331752.jim

These files are created when selecting the demo project option when logging into the JIRA instance for the first time.

This happened exporting from JIRA 5.2.2 running locally, and importing into JIRA 6.0-OD-1.1 in OnDemand.