Fixes case where endPosition === startPosition

[Kronuz]

Some times, when endPosition is equal to startPosition, length ends up being zero.

This makes language server (I'm using javascript-typescript-langserver) give wrong diagnostics
flagging the problem at position (0, 0).

space-in-parens error is an example:

    import('./test3' /* webpackChunkName: "test3" */).then(({ test3 }) => {
      test3('first');
    });