fix(language-core): add undefined to first param type of optional model emits

[KazariEX]

fix vuejs/core#12817

[pkg-pr-new]

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vue-component-meta

npm i https://pkg.pr.new/vuejs/language-tools/vue-component-meta@5171

@vue/language-plugin-pug

npm i https://pkg.pr.new/vuejs/language-tools/@vue/language-plugin-pug@5171

@vue/language-server

npm i https://pkg.pr.new/vuejs/language-tools/@vue/language-server@5171

@vue/language-core

npm i https://pkg.pr.new/vuejs/language-tools/@vue/language-core@5171

@vue/language-service

npm i https://pkg.pr.new/vuejs/language-tools/@vue/language-service@5171

vue-tsc

npm i https://pkg.pr.new/vuejs/language-tools/vue-tsc@5171

@vue/typescript-plugin

npm i https://pkg.pr.new/vuejs/language-tools/@vue/typescript-plugin@5171

vue-component-type-helpers

npm i https://pkg.pr.new/vuejs/language-tools/vue-component-type-helpers@5171

commit: 2f9a020