fix(compiler-core): recognize empty string as non-identifier

[KazariEX]

https://play.vuejs.org/#eNp9kLuOwjAQRX8lmpoNxW6FIqTdFQUUgIDSTZQMweB4LHscIqH8O7YRjwLR2fecse74Ar/G5J1HmEDB2BpVMk6FzrKill3Wfe2J8mkxDpeQFuMXBUbAriK9l01+dKTDC5c4KKCi1kiFdmVYknYCJlkikZVK0XmRMrYeR/e8OmB1epMfXR8zAWuLDm2HAh6MS9sg3/Bsu8Q+nB+wpdqrYH+AG3SkfOx40/68rkPtFy+1nbeGLEvd7NysZ9TuvlQsGs0h+QLCN/5/WP1Z9zv/SXNCDzBcAU2TfbA=

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB	37.9 kB	34.2 kB
vue.global.prod.js	158 kB (+3 B)	57.8 kB (+4 B)	51.4 kB (+10 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.6 kB	18.3 kB	16.7 kB
createApp	54.6 kB	21.3 kB	19.4 kB
createSSRApp	58.7 kB	23 kB	20.9 kB
defineCustomElement	59.4 kB	22.8 kB	20.8 kB
overall	68.4 kB	26.4 kB	24 kB

[pkg-pr-new]

Open in Stackblitz

@vue/compiler-core

npm i https://pkg.pr.new/@vue/compiler-core@12553

@vue/compiler-sfc

npm i https://pkg.pr.new/@vue/compiler-sfc@12553

@vue/compiler-dom

npm i https://pkg.pr.new/@vue/compiler-dom@12553

@vue/compiler-ssr

npm i https://pkg.pr.new/@vue/compiler-ssr@12553

@vue/runtime-core

npm i https://pkg.pr.new/@vue/runtime-core@12553

@vue/runtime-dom

npm i https://pkg.pr.new/@vue/runtime-dom@12553

@vue/reactivity

npm i https://pkg.pr.new/@vue/reactivity@12553

@vue/server-renderer

npm i https://pkg.pr.new/@vue/server-renderer@12553

@vue/shared

npm i https://pkg.pr.new/@vue/shared@12553

vue

npm i https://pkg.pr.new/vue@12553

@vue/compat

npm i https://pkg.pr.new/@vue/compat@12553

commit: c9baf56