fix(reactivity): trigger reactivity for Map key undefined

[jh-leong]

close #12054

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB (+17 B)	38.1 kB (+6 B)	34.2 kB (+30 B)
vue.global.prod.js	160 kB (+17 B)	58 kB (+5 B)	51.5 kB (-39 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	49.1 kB (+17 B)	18.9 kB (+5 B)	17.3 kB (+6 B)
createApp	55.7 kB (+17 B)	21.4 kB (+5 B)	19.6 kB (-32 B)
createSSRApp	59.7 kB (+17 B)	23.1 kB (+6 B)	21 kB (+17 B)
defineCustomElement	60.5 kB (+17 B)	23 kB (+4 B)	20.9 kB (-5 B)
overall	69.4 kB (+17 B)	26.5 kB (+5 B)	24.1 kB (+1 B)

[pkg-pr-new]

Open in Stackblitz

@vue/compiler-dom

pnpm add https://pkg.pr.new/@vue/compiler-dom@12055

@vue/compiler-core

pnpm add https://pkg.pr.new/@vue/compiler-core@12055

@vue/compiler-sfc

pnpm add https://pkg.pr.new/@vue/compiler-sfc@12055

@vue/compiler-ssr

pnpm add https://pkg.pr.new/@vue/compiler-ssr@12055

@vue/reactivity

pnpm add https://pkg.pr.new/@vue/reactivity@12055

@vue/runtime-dom

pnpm add https://pkg.pr.new/@vue/runtime-dom@12055

@vue/runtime-core

pnpm add https://pkg.pr.new/@vue/runtime-core@12055

@vue/shared

pnpm add https://pkg.pr.new/@vue/shared@12055

@vue/server-renderer

pnpm add https://pkg.pr.new/@vue/server-renderer@12055

vue

pnpm add https://pkg.pr.new/vue@12055

@vue/compat

pnpm add https://pkg.pr.new/@vue/compat@12055

commit: b05aa80

[jh-leong]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	❌ failure	❌ failure
nuxt	✅ success	✅ success
pinia	✅ success	✅ success
primevue	✅ success	✅ success
quasar	✅ success	✅ success
radix-vue	✅ success	✅ success
router	✅ success	✅ success
test-utils	✅ success	✅ success
vant	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vue-macros	❌ failure	❌ failure
vuetify	✅ success	✅ success
vueuse	❌ failure	❌ failure
vue-simple-compiler	✅ success	✅ success