List of steps to reproduce (step by step, including full links if applicable):

• open gutenberg wikipedia-preview editor
• open the language selector (look for language code)
• select "winaray" from the default languages
• then type in «awfw»
• (also: «espanlea» in english is another case)

What happens?:

• loading hangs
• see this error in console [1]

What should have happened instead?:

• handle the error gracefully and not remain hanging on loading

[1]

Uncaught TypeError: page is undefined
    fulltextSearch api.js:71
    fulltextSearch api.js:64
    request api.js:111
    request api.js:110
    fulltextSearch api.js:58
    InlineEditUI inline.js:40
    prefixSearch api.js:21
    request api.js:111
    request api.js:110
    prefixSearch api.js:19
    InlineEditUI inline.js:38