What steps will reproduce the problem?
1. Create a raid in a multi-difficulty instance, e.g. Trial of the Crusader
2. Click on "export" button to export in XML format from a frFR WoW Client (not tested with other languages)

What is the expected output? What do you see instead?
First click fires an error, subsequent clicks fire nothing

What version of the product are you using?
1.6.0

Do you have an error log of what happened?
a) Apparently the bug is with multi-difficulty instances: I can export Ulduar raids, and I can export in formats other than XML
Issue seems to be with
if (difficulty and HeadCount.INSTANCES[raidZone].hasMultiDifficulty) then
in HeadCountFrames.lua

b) As the problem might be a localization issue, I've checked that by creating a locale/fr_FR.lua file, added it in HeadCount.toc, and translated "Trial of the Crusader" to french "épreuve du croisé". Then, HeadCount detects the raid zone, but the bug is still there.
When using enUS default HeadCount version, Trial of the Crusader is not recognized (whereas Ulduar is, as it's the same in english and french)

Please provide any additional information below.
The bug is quite recent, as I've been able to export Trial of C. raids in the past. XML file was correct, I just had to manually add <zone> as it was empty due to localization. I've updated HeadCount to r100 but it did not fix anything.