Fix irrelevant duplicate data mixin

[igk1972]

Fix problem after merge multiple data objects (with different keys).

The problem occurs when you use pagination on pages where some fields are missing.
Vue merges multiple data mixins, so the data contains irrelevant fields.

[zachleat]

Ah, can you describe the problem a little bit more? What do you mean multiple data objects? I’d love to get a test around this before I merge

[igk1972]

Ah, can you describe the problem a little bit more? What do you mean multiple data objects? I’d love to get a test around this before I merge

Short.
When we use pagination on pages, then vue-component rendered many times and many places. But data object may be empty.
See https://github.com/11ty/eleventy-plugin-vue/blob/master/EleventyVue.js#L323

I will to create special repository example. Later, on this week.