Messages sent through Lightspeed clients intermittently fail to parse

[Coffeeist]

Related to this issue from Miscord - noting here as it seems to be handled within this codebase.

Lightspeed clients - iOS per the linked issue as well as facebook.com/messenger desktop browser site on my side at the least - appear to add some randomized gibberish in front of message data, causing message parsing to fail:

Error while parsing the following message: (�9hjaimLxSMet4EwK36vf9A�{"deltas":[{"deltaNewMessage":{"messageMetadata":{"threadKey":{"threadFbId":1503335003032641},"messageId":"mid.$gAAVXRnTVjEF_V0jSTF5JgOIPszg1","offlineThreadingId":6794103221279471669,"actorFbId":1636270833,"timestamp":1619840436812,"shouldBuzzDevice":true,"tags":["source:chat:light_speed","app_id:2220391788200892"],"threadReadStateEffect":2,"skipBumpThread":false,"cid":{"conversationFbid":1503335003032641}},"body":"test","attachments":[]}}],"firstDeltaSeqId":265093,"lastIssuedSeqId":265093,"queueEntityId":100034260730370} Error while parsing the following message: (�9hjaimLxSMet4EwK36vf9A�

This seems to be randomized such that it does not always insert problematic characters, as it does work fine more often than not in my experience.

Suggestion for a fix:
It seems that the actual data after after the gibberish string consistently starts with {"deltas": - as such I wonder if cutting out everything before {"deltas": would resolve the issue. In my head this would be something like:
ms = ((ms.indexOf('{"deltas"') > 0) ? ms.substr(ms.indexOf('{"deltas"')) : ms) right above here https://github.com/ChatPlug/libfb-js/blob/master/src/Client.ts#L312

Will test myself if I get a chance

[Coffeeist]

Can't add a branch/PR so I made a gist of /src/Client.ts with the added line, highlighted here:
https://gist.github.com/Coffeeist/593468fe22dfe6d4ba8a94296ec32c96#file-clients-ts-L312

Tested with multiple users (lightspeed to confirm fix, non lightspeed to regression test) without issue in a bridged group of around 20 people