fix: webpack5 externalsType.script add vue.js

[maotong06]

fix webpack dev runtime on use externalsType.script;

review bug:
webpack config this:

externalsType: 'script',
externals: {
  vue: ['https://cdn.jsdelivr.net/npm/vue@2.7.10/dist/vue.js', 'Vue'],
},

then, this has error in console
TypeError: Cannot read properties of undefined (reading 'split')
and can not render vue anymore.

[maotong06]

init by Vue2 and vue cli