Give `{}` some other type than `{}` so it doesn't cause subtype reduction problems with primitives

<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common "Bugs" That Aren't Bugs section! Please help us by doing the following steps before logging an issue: * Search: https://github.com/Microsoft/TypeScript/search?type=Issues * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ Please fill in the *entire* template below. --> <!-- Please try to reproduce the issue with the latest published version. It may have already been fixed. For npm: `typescript@next` This is also the 'Nightly' version in the playground: http://www.typescriptlang.org/play/?ts=Nightly --> **TypeScript Version:** 3.9.0-beta <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** Array **Code** ```ts let a = [{a:1},1,2,3] // OK, Expected (number | { a: number; })[] let b = [{},1,2,3] // Error, Expected: `({}|1)[]` Actual: `{}[]` ``` **Playground Link:** [Playground Link](https://www.typescriptlang.org/play?ts=3.9.0-beta#code/FAGwpgLgBAhlC8UDaBvGAuAjAXwDSdwCZcBmAXSgHpKoB5AaVygFEAPABzAGMIwATKAAoAdgFcAtgCMwAJygAfKCljooYqbIDcUbAEokZUJCiSEyFHgLFyVGsxkyA9jKYsO3Xn1UADQRfmY+mTeUACCPKIwID4WBt5AA) **Related Issues:** <!-- Did you find other bugs that looked similar? -->