Unable to send ctrl-underscore (ascii 0x1f) from Hacker's Keyboard

[badfish]

Using connectbot 1.9.8-oss and hacker's keyboard from F-Droid: ssh to any server and press ctrl-shift-underscore. Should send ascii 0x1f. Actual behaviour depends on settings: either sends underscore or reduces the beep volume.

See the linked pull request for further explanation and proposed fix.