Uncaught TypeError: u.toLowerCase is not a function

[czxin788]

when I type word in the editor window, It return errors,how can i do?

    Uncaught TypeError: u.toLowerCase is not a function
    at c.filterCompletions (ext-language_tools.js:1:31287)
    at c.setFilter (ext-language_tools.js:1:30762)
    at l.<anonymous> (ext-language_tools.js:1:28080)
    at ext-language_tools.js:1:26824
    at Object.getCompletions (ace-init.js:56:24)
    at ext-language_tools.js:1:26764
    at Array.forEach (<anonymous>)
    at l.gatherCompletions (ext-language_tools.js:1:26740)
    at l.updateCompletions (ext-language_tools.js:1:27754)
    at l.showPopup (ext-language_tools.js:1:27223)