Quick reply/replyAll fails if identity has null doCcList or doBccList

[nauhygon]

Whenever I hit the quick Reply or ReplyAll button, the To and Cc fields were not populated. In the Error console, I saw this error message:

Error: [Exception... "'TypeError: aDefault is null' when calling method: [nsIStreamListener::onStopRequest]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "native frame :: :: <TOP_LEVEL> :: line 0" data: no]

Digging a little deeper, I found that in stub.composed-ui.js, the identity in ComposeSession instance has doCc set to true, but doCcList to null. This fails mergeDefault() in changeComposeFields(), leaving the To, Cc, and Bcc fields unfilled.

I am not sure if this is also happening to others. Looking through the issues, I am not seeing this particular issue. It may have been just a very special case for me as in about::config, I don't see mail.identity..doCcList.

Fix seems simple and hopefully safe. I will supply a patch shortly.

[protz]

Patch merged, thanks for the detailed explanation and rationale!