sftp.fastGet sometimes throws an exception that can't be caught

[metalgrid]

Hi,
I've an app that opens multiple simultaneous ssh2 connections and uses sftp.fastGet to retrieve a set of files in a try/catch block. However, sometimes the program bails with:

TypeError [ERR_INVALID_CALLBACK]: Callback must be a function
    at maybeCallback (fs.js:128:9)
    at Object.write (fs.js:535:14)
    at onread (/home/iskren/Projects/grapher/node_modules/ssh2-streams/lib/sftp.js:1120:17)
    at cb (/home/iskren/Projects/grapher/node_modules/ssh2-streams/lib/sftp.js:899:7)
    at SFTPStream._transform (/home/iskren/Projects/grapher/node_modules/ssh2-streams/lib/sftp.js:417:17)
    at SFTPStream.Transform._read (_stream_transform.js:190:10)
    at SFTPStream._read (/home/iskren/Projects/grapher/node_modules/ssh2-streams/lib/sftp.js:183:15)
    at SFTPStream.Transform._write (_stream_transform.js:178:12)
    at doWrite (_stream_writable.js:410:12)
    at writeOrBuffer (_stream_writable.js:394:5)

At other times it works as intended and at third times it just leaves an open ssh connection without any data goin through it but that's probably for another issue.

Using ssh2-streams 0.4.2 with node v10.15.3