Comment 0 for bug 454166

We moved our system langpacks from one location to another - previously not used one - for karmic; this seemed to have cause extension manager to go into a bad state (at least for me).

The symptoms are that during the upgrade, the uninstallItem function fails here:

http://hg.mozilla.org/mozilla-central/file/dbebe1771118/toolkit/mozapps/extensions/src/nsExtensionManager.js.in#l4591

with an exception like:

[Exception... "Could not convert JavaScript argument arg 1 [nsIRDFDataSource.GetTarget]" nsresult: "0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)" location: "JS frame :: file:///usr/lib/xulrunner-1.9.1.5pre/components/nsExtensionManager.js :: EMDS__setProperty :: line 7250" data: no]

... which breaks the whole extension update somewhat.

I looked a bit around thinking that maybe the UPGRADE op is wrong, but i think thats not the problem. It seems that the _setProperty code her:

http://hg.mozilla.org/mozilla-central/file/dbebe1771118/toolkit/mozapps/extensions/src/nsExtensionManager.js.in#l6939

is supposed to deal with this situation as it explicitly tests "if (oldValue)" ... however, GetTarget does not return null but throws and exception, so a potential fix would be to just catch it there.