Typing a backslash while searching for a file shows an error

[rsyh93]

To Reproduce
Steps to reproduce the behavior:

While browsing the filesystem normally,

1. Type any letter (e.g. 'k') to start the search
2. Type the '\' character
3. See error in dialog box

Expected behavior
No error; continue searching for a file with \ character.

Screenshots

SyntaxError: Invalid regular expression: /k\/: \ at end of pattern
   at new RegExp (<anonymous>)
   at Object.searchFile (/home/young/Projects/mdir.js/build/panel_blassed/BlessedPanel.js:362:27)
   at Object.keyInputSearchFile (/home/young/Projects/mdir.js/build/panel_blassed/BlessedPanel.js:238:18)
   at processTicksAndRejections (internal/process/task_queues.js:97:5)
   at async Screen.<anonymous> (/home/young/Projects/mdir.js/build/panel_blassed/BaseMainFrame.js:402:36)

Desktop (please complete the following information):

• OS: Ubuntu Linux 21.04

[la9527]

I have reflected it in version 1.2.7.
Thank you for providing multiple patches.