Fix completions

[Rob Anderson]

When typing the server is failing to generate completions. For instance adding r to examples/server.ts's for loop, which should complete to req produces this error:

Unable to get completion info from TypeScript: Error: Debug Failure. Illegal value: "r"
  at isValidTrigger (deno:cli/tsc/00_typescript.js:122443:37)
  at Object.getCompletionsAtPosition (deno:cli/tsc/00_typescript.js:120179:92)
  at Object.getCompletionsAtPosition (deno:cli/tsc/00_typescript.js:149797:35)
  at serverRequest (deno:cli/tsc/99_main_compiler.js:632:27)
  at [native_code]:1:12

Internal error

The code:

import * as http from "https://deno.land/std@0.97.0/http/server.ts";

const server = http.serve({ port: 8000 });

console.log("http://localhost:8000/");

for await (const req of server) {
  // req.respond({ body: "Hello World\n" });
  r
}

[Rob Anderson]

I requested help from deno ~ denoland/deno#10966
and submitted a Nova bug report ~ https://devforum.nova.app/t/bug-with-textdocument-completion/969